link to install docs instead of launchpad downloads

Author: obfuscurity

_includes/page-header.html

@@ -32,7 +32,7 @@
           </a>
         </li> -->
         <li class="site-nav__item">
-          <a class="site-nav__button btn btn--primary" href="https://launchpad.net/graphite/+download" target="_blank">Download</a>
+          <a class="site-nav__button btn btn--primary" href="http://graphite.readthedocs.io/en/latest/install.html" target="_blank">Install</a>
         </li>
       </ul>
     </nav>