Merge branch 'master' into v4

Conflicts:
	Gruntfile.js
	_config.yml
	dist/css/bootstrap-theme.css
	dist/css/bootstrap-theme.min.css
	dist/css/bootstrap.css
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	dist/fonts/glyphicons-halflings-regular.eot
	dist/fonts/glyphicons-halflings-regular.svg
	dist/fonts/glyphicons-halflings-regular.ttf
	dist/fonts/glyphicons-halflings-regular.woff
	docs/_data/glyphicons.yml
	docs/_includes/components/alerts.html
	docs/_includes/components/badges.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/labels.html
	docs/_includes/components/media.html
	docs/_includes/components/navbar.html
	docs/_includes/components/navs.html
	docs/_includes/components/pagination.html
	docs/_includes/components/panels.html
	docs/_includes/components/progress-bars.html
	docs/_includes/css/buttons.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/responsive-utilities.html
	docs/_includes/css/sass.html
	docs/_includes/css/tables.html
	docs/_includes/css/type.html
	docs/_includes/getting-started/accessibility.html
	docs/_includes/getting-started/browser-device-support.html
	docs/_includes/getting-started/community.html
	docs/_includes/getting-started/download.html
	docs/_includes/getting-started/examples.html
	docs/_includes/getting-started/whats-included.html
	docs/_includes/js/affix.html
	docs/_includes/js/alerts.html
	docs/_includes/js/buttons.html
	docs/_includes/js/carousel.html
	docs/_includes/js/collapse.html
	docs/_includes/js/dropdowns.html
	docs/_includes/js/modal.html
	docs/_includes/js/overview.html
	docs/_includes/js/tabs.html
	docs/_includes/nav/components.html
	docs/_includes/nav/css.html
	docs/_includes/nav/javascript.html
	docs/_includes/nav/main.html
	docs/about.html
	docs/assets/css/docs.min.css
	docs/assets/js/customize.min.js
	docs/assets/js/raw-files.min.js
	docs/dist/css/bootstrap-theme.css
	docs/dist/css/bootstrap-theme.min.css
	docs/dist/css/bootstrap.css
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css
	docs/dist/fonts/glyphicons-halflings-regular.eot
	docs/dist/fonts/glyphicons-halflings-regular.svg
	docs/dist/fonts/glyphicons-halflings-regular.ttf
	docs/dist/fonts/glyphicons-halflings-regular.woff
	docs/examples/carousel/index.html
	docs/examples/navbar-fixed-top/index.html
	docs/examples/navbar-static-top/index.html
	docs/examples/navbar/index.html
	docs/examples/non-responsive/index.html
	docs/examples/non-responsive/non-responsive.css
	docs/examples/sticky-footer-navbar/index.html
	docs/examples/theme/index.html
	fonts/glyphicons-halflings-regular.eot
	fonts/glyphicons-halflings-regular.svg
	fonts/glyphicons-halflings-regular.ttf
	fonts/glyphicons-halflings-regular.woff
	less/_carousel.less
	less/_forms.less
	less/glyphicons.less

docs/components/input-group.md

@@ -122,7 +122,7 @@ 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 dropdown-toggle" data-toggle="dropdown">Action</button>
+        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" aria-expanded="false">Action</button>
         <ul class="dropdown-menu" role="menu">
           <li><a href="#">Action</a></li>
           <li><a href="#">Another action</a></li>
@@ -138,7 +138,7 @@ Buttons in input groups are a bit different and require one extra level of nesti
     <div class="input-group">
       <input type="text" class="form-control">
       <div class="input-group-btn">
-        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown">Action</button>
+        <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">
           <li><a href="#">Action</a></li>
           <li><a href="#">Another action</a></li>
@@ -160,7 +160,7 @@ Buttons in input groups are a bit different and require one extra level of nesti
     <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">
+        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" tabindex="-1" aria-expanded="false">
           <span class="sr-only">Toggle Dropdown</span>
         </button>
         <ul class="dropdown-menu" role="menu">
@@ -179,7 +179,7 @@ Buttons in input groups are a bit different and require one extra level of nesti
       <input type="text" class="form-control">
       <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">
+        <button type="button" class="btn btn-secondary dropdown-toggle" data-toggle="dropdown" tabindex="-1" aria-expanded="false">
           <span class="sr-only">Toggle Dropdown</span>
         </button>
         <ul class="dropdown-menu dropdown-menu-right" role="menu">