Swap out sponsorship page with donation page in top nav

Not sure why "Donate" went to the sponsorship page in the first place.

Author: mxie

_includes/topbar.html

@@ -34,7 +34,7 @@
             <li><a target="_blank" href="https://docs.google.com/forms/d/e/1FAIpQLSeJRT5PHqRsQ-gwgIAOMZCOb6WCiZgQ0h8Kgf2y6vXNqieoUw/viewform">Help Make Stuff Happen</a></li>
           </ul>
         </li>
-        <li><a href="/sponsor">Donate</a></li>
+        <li><a href="/donate">Donate</a></li>
       </ul>
     </div><!--/.nav-collapse -->
 </div>