Update readme.md

Author: benoitongit

README.md

@@ -24,8 +24,15 @@ Or install it yourself as:
 
     $ gem install vue_on_rails
 
+Note that this gem requires vue.js, it must be included in your app.
+
 ## Usage
 
+Require vue_on_rails in application.js
+```
+//= require vue_on_rails
+```
+
 Init and destroy Vue components:
 ```
 # Load Vue components