Add aria-hidden to icons in about page

Author: patrickhlauke

docs/about.html

@@ -99,17 +99,17 @@ <h2>Name</h2>
   <div class="bs-brand-logos">
     <div class="bs-brand-item">
       <h3>Bootstrap</h3>
-      <span class="glyphicon glyphicon-ok"></span>
+      <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
       <span class="sr-only">(correct)</span>
     </div>
     <div class="bs-brand-item">
       <h3 class="text-muted">BootStrap</h3>
-      <span class="glyphicon glyphicon-remove"></span>
+      <span class="glyphicon glyphicon-remove" aria-hidden="true"></span>
       <span class="sr-only">(incorrect)</span>
     </div>
     <div class="bs-brand-item">
       <h3 class="text-muted">Twitter Bootstrap</h3>
-      <span class="glyphicon glyphicon-remove"></span>
+      <span class="glyphicon glyphicon-remove" aria-hidden="true"></span>
       <span class="sr-only">(incorrect)</span>
     </div>
   </div>