Remove sr-only from components/dropdown entirely

possibly less confusing option, as per discussion, is to always show the
dropdown trigger button (both live and in that code example)

docs/_includes/components/dropdowns.html

@@ -7,8 +7,8 @@
   <p>Wrap the dropdown's trigger and the dropdown menu within <code>.dropdown</code>, or another element that declares <code>position: relative;</code>. Then add the menu's HTML.</p>
   <div class="bs-example">
     <div class="dropdown clearfix">
-      <button class="btn dropdown-toggle sr-only" type="button" id="dropdownMenu1" data-toggle="dropdown">
-        Dropdown trigger
+      <button class="btn dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown">
+        Dropdown
         <span class="caret"></span>
       </button>
       <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
@@ -23,7 +23,7 @@
 {% highlight html %}
 <div class="dropdown">
   <button class="btn dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown">
-    Dropdown trigger
+    Dropdown
     <span class="caret"></span>
   </button>
   <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
@@ -56,7 +56,7 @@
   <p>Add a header to label sections of actions in any dropdown menu.</p>
   <div class="bs-example">
     <div class="dropdown clearfix">
-      <button class="btn dropdown-toggle sr-only" type="button" id="dropdownMenu2" data-toggle="dropdown">
+      <button class="btn dropdown-toggle" type="button" id="dropdownMenu2" data-toggle="dropdown">
         Dropdown
         <span class="caret"></span>
       </button>
@@ -85,7 +85,7 @@
   <p>Add <code>.disabled</code> to a <code>&lt;li&gt;</code> in the dropdown to disable the link.</p>
   <div class="bs-example">
     <div class="dropdown clearfix">
-      <button class="btn dropdown-toggle sr-only" type="button" id="dropdownMenu3" data-toggle="dropdown">
+      <button class="btn dropdown-toggle" type="button" id="dropdownMenu3" data-toggle="dropdown">
         Dropdown
         <span class="caret"></span>
       </button>