Update website to link to OkHttp 3.x Javadoc.

Author: squarejesse

website/index.html

@@ -150,7 +150,7 @@ <h3 id="license">License</h3>
               </ul>
               <ul class="nav nav-pills nav-stacked secondary">
                 <li><a href="https://github.com/square/okhttp/wiki">Wiki</a></li>
-                <li><a href="2.x/okhttp/">Javadoc</a></li>
+                <li><a href="3.x/okhttp/">Javadoc</a></li>
                 <li><a href="http://stackoverflow.com/questions/tagged/okhttp?sort=active">StackOverflow</a></li>
               </ul>
             </div>