Enable dropdown in sticky-footer with Bootstrap JS

The sticky-footer example uses a drop down in its navbar, and dropdowns
require Bootstrap's JS to work.

Use the minified version of Bootstrap since this example is about the
CSS and not about the JS.

sticky-footer-navbar/index.html

@@ -67,5 +67,9 @@
       </div>
     </div>
 
+    <!-- Bootstrap core JavaScript
+    ================================================== -->
+    <script src="../assets/js/jquery.js"></script>
+    <script src="../bootstrap/js/bootstrap.min.js"></script>
   </body>
 </html>
\ No newline at end of file