Proper example for bootstrap input groups

Closes #2241

src/_includes/examples/bootstrap.html

@@ -22,11 +22,11 @@
       </div>
       <div class="margin-bottom">
         <div class="input-group margin-bottom-sm">
-          <span class="input-group-addon"><i class="fa fa-envelope-o"></i></span>
+          <span class="input-group-addon"><i class="fa fa-envelope-o fa-fw"></i></span>
           <input class="form-control" type="text" placeholder="Email address">
         </div>
         <div class="input-group">
-          <span class="input-group-addon"><i class="fa fa-key"></i></span>
+          <span class="input-group-addon"><i class="fa fa-key fa-fw"></i></span>
           <input class="form-control" type="password" placeholder="Password">
         </div>
       </div>
@@ -67,11 +67,11 @@
 </div>
 
 <div class="input-group margin-bottom-sm">
-  <span class="input-group-addon"><i class="fa fa-envelope-o"></i></span>
+  <span class="input-group-addon"><i class="fa fa-envelope-o fa-fw"></i></span>
   <input class="form-control" type="text" placeholder="Email address">
 </div>
 <div class="input-group">
-  <span class="input-group-addon"><i class="fa fa-key"></i></span>
+  <span class="input-group-addon"><i class="fa fa-key fa-fw"></i></span>
   <input class="form-control" type="password" placeholder="Password">
 </div>