Add link to GitHub page

Author: Sunderlandkyl

_includes/themes/twitter/top.html

@@ -39,6 +39,11 @@ <h2>Contact</h2>
     <p>How to cite, where to report errors, ask questions, or get more information.</p>
     <p><a class="btn" href="contact.html">View contact information &raquo;</a></p>
   </div>
+  <div class="span4">
+    <h2>GitHub</h2>
+    <p>See the source code on GitHub.</p>
+    <p><a class="btn" href="https://github.com/PlusToolkit/PlusLib"><i class="images/GitHub-Mark-Light-32px.png"></i>View source code &raquo;</a></p>
+  </div>
 </div>
 
 <div class="row-fluid">