update cover

Author: yussan

README.md

@@ -1,7 +1,7 @@
 # aoi-php
 PHP micro framework to help build your MVC project with minimal code flow.
 
-![aoi php cover](https://pbs.twimg.com/media/DKKQTInUMAE9xJk.jpg:large)
+![pure php mvc cover](http://res.cloudinary.com/dhjkktmal/image/upload/v1520304797/github/pure-php-mvc.png)
 
 ## Prerequisites
 - Composer <a target="_blank" href="https://getcomposer.org/">read more</a>