Switch to jQuery 2.1.4.

Now that we don't support IE 8 it's safe to do that.

docs/_includes/footer.html

@@ -11,7 +11,7 @@
   </div>
 </footer>
 
-<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
+<script src="{{ site.cdn.jquery }}"></script>
 <script>window.jQuery || document.write('<script src="{{ site.baseurl }}/assets/js/vendor/jquery.min.js"><\/script>')</script>
 
 {% if site.github %}