Fix element structure

Change end tag from </div> to </h4> to correctly match opening tag

examples/responsive.html

@@ -465,7 +465,7 @@
               Lena
               <div class="sub header">Human Resources
             </div>
-          </div>
+          </h4>
         </td>
         <td>
           22
@@ -479,7 +479,7 @@
               Matthew
               <div class="sub header">Fabric Design
             </div>
-          </div>
+          </h4>
         </td>
         <td>
           15
@@ -493,7 +493,7 @@
               Lindsay
               <div class="sub header">Entertainment
             </div>
-          </div>
+          </h4>
         </td>
         <td>
           12
@@ -507,7 +507,7 @@
               Mark
               <div class="sub header">Executive
             </div>
-          </div>
+          </h4>
         </td>
         <td>
           11