Update the link to ROR doctrine (#531)

Author: ahangarha

app/views/pages/_header.html.erb

@@ -20,7 +20,7 @@
     Read <%= link_to "Documentation for React on Rails",
                 "https://shakacode.gitbooks.io/react-on-rails/content/" %> and
     <%= link_to "The React on Rails Doctrine",
-                "http://www.shakacode.com/2016/01/27/the-react-on-rails-doctrine.html" %>.
+                "https://www.shakacode.com/blog/the-react-on-rails-doctrine" %>.
   </li>
   <li>
     See our React Native Client: