improve accessibility

* add 'aria-label' into some elements without the label
* add 'aris-label' into some visual elements
* replace some 'a' elements have a button action to 'button'

app/views/admin/get_all_users.html.erb

@@ -26,7 +26,7 @@
               <%= u.email%>
             </td>
             <td>
-              <%= u.admin ? %{<span class="fs1" aria-hidden="true" data-icon="&#xe0fe;"}.html_safe : nil %>
+              <%= u.admin ? %{<span class="fs1" aria-label="check" data-icon="&#xe0fe;"}.html_safe : nil %>
             </td>
             <td>
               <%= link_to "Edit", "#", {:onClick => "javascript:openEditModal(#{u.id});", :role => "button", :style => "width:70px", :class => "btn btn-inverse", "data-toggle" => "modal"}%>

app/views/admin/get_user.html.erb

@@ -1,6 +1,6 @@
 <!-- Begin Modal -->
     <div class="modal-header">
-      <button type="button" class="close" data-dismiss="modal" aria-hidden="true">
+      <button type="button" class="close" data-dismiss="modal" aria-label="dismiss">
         ×
       </button>
       <h4 id="myModalLabel1">