Merge branch 'master' into v4

Conflicts:
	Gruntfile.js
	dist/css/bootstrap-theme.css
	dist/css/bootstrap-theme.css.map
	dist/css/bootstrap-theme.min.css
	dist/css/bootstrap.css
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	dist/js/bootstrap.min.js
	docs/_data/glyphicons.yml
	docs/_includes/components/alerts.html
	docs/_includes/components/badges.html
	docs/_includes/components/breadcrumbs.html
	docs/_includes/components/button-dropdowns.html
	docs/_includes/components/button-groups.html
	docs/_includes/components/dropdowns.html
	docs/_includes/components/glyphicons.html
	docs/_includes/components/input-groups.html
	docs/_includes/components/jumbotron.html
	docs/_includes/components/labels.html
	docs/_includes/components/list-group.html
	docs/_includes/components/media.html
	docs/_includes/components/navbar.html
	docs/_includes/components/navs.html
	docs/_includes/components/page-header.html
	docs/_includes/components/pagination.html
	docs/_includes/components/panels.html
	docs/_includes/components/progress-bars.html
	docs/_includes/components/responsive-embed.html
	docs/_includes/components/thumbnails.html
	docs/_includes/components/wells.html
	docs/_includes/css/buttons.html
	docs/_includes/css/code.html
	docs/_includes/css/forms.html
	docs/_includes/css/grid.html
	docs/_includes/css/helpers.html
	docs/_includes/css/images.html
	docs/_includes/css/less.html
	docs/_includes/css/tables.html
	docs/_includes/css/type.html
	docs/_includes/customizer-variables.html
	docs/_includes/getting-started/accessibility.html
	docs/_includes/getting-started/disabling-responsiveness.html
	docs/_includes/getting-started/download.html
	docs/_includes/getting-started/whats-included.html
	docs/_includes/js/alerts.html
	docs/_includes/js/buttons.html
	docs/_includes/js/carousel.html
	docs/_includes/js/collapse.html
	docs/_includes/js/modal.html
	docs/_includes/js/overview.html
	docs/_includes/js/popovers.html
	docs/_includes/js/tabs.html
	docs/_includes/js/tooltips.html
	docs/_includes/nav/components.html
	docs/_includes/nav/javascript.html
	docs/_jade/customizer-variables.jade
	docs/_layouts/default.html
	docs/about.html
	docs/assets/css/docs.min.css
	docs/assets/css/src/docs.css
	docs/assets/js/customize.min.js
	docs/assets/js/raw-files.min.js
	docs/assets/js/src/customizer.js
	docs/customize.html
	docs/dist/css/bootstrap-theme.css.map
	docs/dist/css/bootstrap.css
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css
	less/glyphicons.less
	less/mixins/vendor-prefixes.less
	less/navbar.less
	less/popovers.less
	less/tables.less
	less/theme.less
	less/tooltip.less
	less/variables.less
	package.json
	scss/_carousel.scss
	scss/_close.scss
	scss/_forms.scss
	test-infra/npm-shrinkwrap.json

5 files changed, 42 insertions, 37 deletions

diff --git a/docs/components/alerts.md b/docs/components/alerts.md
index ff25de763..f11f8fbfa 100644
--- a/docs/components/alerts.md
+++ b/docs/components/alerts.md
@@ -33,7 +33,7 @@ Build on any alert by adding an optional `.alert-dismissible` and [close button]
 
 {% example html %}
 <div class="alert alert-warning alert-dismissible" role="alert">
-  <button type="button" class="close" data-dismiss="alert">
+  <button type="button" class="close" data-dismiss="alert" aria-label="Close">
     <span aria-hidden="true">&times;</span>
     <span class="sr-only">Close</span>
   </button>
diff --git a/docs/components/button-group.md b/docs/components/button-group.md
index 80c69b5b9..650949820 100644
--- a/docs/components/button-group.md
+++ b/docs/components/button-group.md
@@ -54,7 +54,7 @@ Combine sets of button groups into button toolbars for more complex components.
 
 ### Sizing
 
-Instead of applying button sizing classes to every button in a group, just add `.btn-group-*` to the `.btn-group`.
+Instead of applying button sizing classes to every button in a group, just add `.btn-group-*` to each `.btn-group`, including each one when nesting multiple groups.
 
 <div class="bs-example">
   <div class="btn-group btn-group-lg" role="group" aria-label="Large button group">
diff --git a/docs/components/helpers.md b/docs/components/helpers.md
index 21a145962..8976e0556 100644
--- a/docs/components/helpers.md
+++ b/docs/components/helpers.md
@@ -52,7 +52,7 @@ Similar to the contextual text color classes, easily set the background of an el
 Use a generic close icon for dismissing content like modals and alerts. **Be sure to include screen reader text when you can** as we've done with `.sr-only`.
 
 {% example html %}
-<button type="button" class="close">
+<button type="button" class="close" aria-label="Close">
   <span aria-hidden="true">&times;</span>
   <span class="sr-only">Close</span>
 </button>
diff --git a/docs/components/input-group.md b/docs/components/input-group.md
index 7da1432c7..fc91ac978 100644
--- a/docs/components/input-group.md
+++ b/docs/components/input-group.md
@@ -17,6 +17,11 @@ Extend form controls by adding text or buttons before, after, or on both sides o
   <h4>Don't mix with other components</h4>
   <p>Do not mix form groups or grid column classes directly with input groups. Instead, nest the input group inside of the form group or grid-related element.</p>
 </div>
+<div class="bs-callout bs-callout-warning" id="callout-inputgroup-form-labels">
+  <h4>Always add labels</h4>
+  <p>Screen readers will have trouble with your forms if you don't include a label for every input. For these input groups, ensure that any additional label or functionality is conveyed to assistive technologies.</p>
+  <p>The exact technique to be used (<code>&lt;label&gt;</code> elements hidden using the <code>.sr-only</code> class, or use of the <code>aria-label</code>, <code>aria-labelledby</code>, <code>aria-describedby</code>, <code>title</code> or <code>placeholder</code> attribute) and what additional information will need to be conveyed will vary depending on the exact type of interface widget you're implementing. The examples in this section provide a few suggested, case-specific approaches.</p>
+</div>
 
 ## Basic example
 
@@ -28,18 +33,18 @@ Place one add-on or button on either side of an input. You may also place one on
 
 {% example html %}
 <div class="input-group">
-  <span class="input-group-addon">@</span>
-  <input type="text" class="form-control" placeholder="Username">
+  <span class="input-group-addon" id="basic-addon1">@</span>
+  <input type="text" class="form-control" placeholder="Username" aria-describedby="basic-addon1">
 </div>
 <br>
 <div class="input-group">
-  <input type="text" class="form-control">
-  <span class="input-group-addon">.00</span>
+  <input type="text" class="form-control" placeholder="Recipient's username" aria-describedby="basic-addon2">
+  <span class="input-group-addon" id="basic-addon2">.00</span>
 </div>
 <br>
 <div class="input-group">
   <span class="input-group-addon">$</span>
-  <input type="text" class="form-control">
+  <input type="text" class="form-control" aria-label="Amount (to the nearest dollar)">
   <span class="input-group-addon">.00</span>
 </div>
 {% endexample %}
@@ -50,18 +55,18 @@ Add the relative form sizing classes to the `.input-group` itself and contents w
 
 {% example html %}
 <div class="input-group input-group-lg">
-  <span class="input-group-addon">@</span>
-  <input type="text" class="form-control" placeholder="Username">
+  <span class="input-group-addon" id="sizing-addon1">@</span>
+  <input type="text" class="form-control" placeholder="Username" aria-describedby="sizing-addon1">
 </div>
 <br>
 <div class="input-group">
-  <span class="input-group-addon">@</span>
-  <input type="text" class="form-control" placeholder="Username">
+  <span class="input-group-addon" id="sizing-addon2">@</span>
+  <input type="text" class="form-control" placeholder="Username" aria-describedby="sizing-addon2">
 </div>
 <br>
 <div class="input-group input-group-sm">
-  <span class="input-group-addon">@</span>
-  <input type="text" class="form-control" placeholder="Username">
+  <span class="input-group-addon" id="sizing-addon3">@</span>
+  <input type="text" class="form-control" placeholder="Username" aria-describedby="sizing-addon3">
 </div>
 {% endexample %}
 
@@ -74,17 +79,17 @@ Place any checkbox or radio option within an input group's addon instead of text
   <div class="col-lg-6">
     <div class="input-group">
       <span class="input-group-addon">
-        <input type="checkbox">
+        <input type="checkbox" aria-label="Checkbox for following text input">
       </span>
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with checkbox">
     </div>
   </div>
   <div class="col-lg-6">
     <div class="input-group">
       <span class="input-group-addon">
-        <input type="radio">
+        <input type="radio" aria-label="Radio button for following text input">
       </span>
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with radio button">
     </div>
   </div>
 </div>
@@ -101,12 +106,12 @@ Buttons in input groups are a bit different and require one extra level of nesti
       <span class="input-group-btn">
         <button class="btn btn-secondary" type="button">Go!</button>
       </span>
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" placeholder="Search for...">
     </div>
   </div>
   <div class="col-lg-6">
     <div class="input-group">
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" placeholder="Search for...">
       <span class="input-group-btn">
         <button class="btn btn-secondary" type="button">Go!</button>
       </span>
@@ -131,12 +136,12 @@ Buttons in input groups are a bit different and require one extra level of nesti
           <li><a href="#">Separated link</a></li>
         </ul>
       </div>
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with dropdown button">
     </div>
   </div>
   <div class="col-lg-6">
     <div class="input-group">
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with dropdown button">
       <div class="input-group-btn">
         <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-expanded="false">Action</button>
         <ul class="dropdown-menu dropdown-menu-right" role="menu">
@@ -159,8 +164,8 @@ Buttons in input groups are a bit different and require one extra level of nesti
   <div class="col-lg-6">
     <div class="input-group">
       <div class="input-group-btn">
-        <button type="button" class="btn btn-secondary" tabindex="-1">Action</button>
-        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" tabindex="-1" aria-expanded="false">
+        <button type="button" class="btn btn-secondary">Action</button>
+        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
           <span class="sr-only">Toggle Dropdown</span>
         </button>
         <ul class="dropdown-menu" role="menu">
@@ -171,15 +176,15 @@ Buttons in input groups are a bit different and require one extra level of nesti
           <li><a href="#">Separated link</a></li>
         </ul>
       </div>
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with segmented button dropdown">
     </div>
   </div>
   <div class="col-lg-6">
     <div class="input-group">
-      <input type="text" class="form-control">
+      <input type="text" class="form-control" aria-label="Text input with segmented button dropdown">
       <div class="input-group-btn">
-        <button type="button" class="btn btn-secondary" tabindex="-1">Action</button>
-        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" tabindex="-1" aria-expanded="false">
+        <button type="button" class="btn btn-secondary">Action</button>
+        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
           <span class="sr-only">Toggle Dropdown</span>
         </button>
         <ul class="dropdown-menu dropdown-menu-right" role="menu">
diff --git a/docs/components/pagination.md b/docs/components/pagination.md
index dacc653f7..35cebe435 100644
--- a/docs/components/pagination.md
+++ b/docs/components/pagination.md
@@ -13,7 +13,7 @@ Simple pagination inspired by Rdio, great for apps and search results. The large
 <nav>
   <ul class="pagination">
     <li>
-      <a href="#">
+      <a href="#" aria-label="Previous">
         <span aria-hidden="true">&laquo;</span>
         <span class="sr-only">Previous</span>
       </a>
@@ -24,7 +24,7 @@ Simple pagination inspired by Rdio, great for apps and search results. The large
     <li><a href="#">4</a></li>
     <li><a href="#">5</a></li>
     <li>
-      <a href="#">
+      <a href="#" aria-label="Next">
         <span aria-hidden="true">&raquo;</span>
         <span class="sr-only">Next</span>
       </a>
@@ -41,7 +41,7 @@ Links are customizable for different circumstances. Use `.disabled` for unclicka
 <nav>
   <ul class="pagination">
     <li class="disabled">
-      <a href="#">
+      <a href="#" aria-label="Previous">
         <span aria-hidden="true">&laquo;</span>
         <span class="sr-only">Previous</span>
       </a>
@@ -54,7 +54,7 @@ Links are customizable for different circumstances. Use `.disabled` for unclicka
     <li><a href="#">4</a></li>
     <li><a href="#">5</a></li>
     <li>
-      <a href="#">
+      <a href="#" aria-label="Next">
         <span aria-hidden="true">&raquo;</span>
         <span class="sr-only">Next</span>
       </a>
@@ -69,7 +69,7 @@ You can optionally swap out active or disabled anchors for `<span>`, or omit the
 <nav>
   <ul class="pagination">
     <li class="disabled">
-      <span>
+      <span aria-label="Previous">
         <span aria-hidden="true">&laquo;</span>
         <span class="sr-only">Previous</span>
       </span>
@@ -88,7 +88,7 @@ Fancy larger or smaller pagination? Add `.pagination-lg` or `.pagination-sm` for
 <nav>
   <ul class="pagination pagination-lg">
     <li>
-      <a href="#">
+      <a href="#" aria-label="Previous">
         <span aria-hidden="true">&laquo;</span>
         <span class="sr-only">Previous</span>
       </a>
@@ -97,7 +97,7 @@ Fancy larger or smaller pagination? Add `.pagination-lg` or `.pagination-sm` for
     <li><a href="#">2</a></li>
     <li><a href="#">3</a></li>
     <li>
-      <a href="#">
+      <a href="#" aria-label="Next">
         <span aria-hidden="true">&raquo;</span>
         <span class="sr-only">Next</span>
       </a>
@@ -110,7 +110,7 @@ Fancy larger or smaller pagination? Add `.pagination-lg` or `.pagination-sm` for
 <nav>
   <ul class="pagination pagination-sm">
     <li>
-      <a href="#">
+      <a href="#" aria-label="Previous">
         <span aria-hidden="true">&laquo;</span>
         <span class="sr-only">Previous</span>
       </a>
@@ -119,7 +119,7 @@ Fancy larger or smaller pagination? Add `.pagination-lg` or `.pagination-sm` for
     <li><a href="#">2</a></li>
     <li><a href="#">3</a></li>
     <li>
-      <a href="#">
+      <a href="#" aria-label="Next">
         <span aria-hidden="true">&raquo;</span>
         <span class="sr-only">Next</span>
       </a>