update Readme with Router v4 update info

Author: revathskumar

README.md

@@ -6,6 +6,11 @@
 
 * http://crypt.codemancers.com/posts/2016-09-16-react-server-side-rendering/
 
+## Using React Router v4
+
+Work in progress on branch [react-router-v4-redux](https://github.com/revathskumar/react-server-render/tree/react-router-v4-redux)
+A demo app is hosted on https://server-render-hzoyerpkgh.now.sh
+
 ## Usage
 
 ### Setup