readme updates [skip ci]

Author: bodrovis

README.md

@@ -2,14 +2,15 @@
 
 [![Gem Version](https://badge.fury.io/rb/angular_rails_csrf.svg)](https://badge.fury.io/rb/angular_rails_csrf)
 [![Build Status](https://travis-ci.org/jsanders/angular_rails_csrf.svg)](https://travis-ci.org/jsanders/angular_rails_csrf)
+[![Test Coverage](https://codecov.io/gh/jsanders/angular_rails_csrf/graph/badge.svg)](https://codecov.io/gh/jsanders/angular_rails_csrf)
 
 The AngularJS [ng.$http](http://docs.angularjs.org/api/ng.$http) service has built-in CSRF protection. By default, it looks for a cookie named `XSRF-TOKEN` and, if found, writes its value into an `X-XSRF-TOKEN` header, which the server compares with the CSRF token saved in the user's session.
 
 This project adds direct support for this scheme to your Rails application without requiring any changes to your AngularJS application. It also doesn't require the use of `csrf_meta_tags` to write a CSRF token into your page markup, so it works for pure JSON API applications.
 
 Note that there is nothing AngularJS specific here, and this will work with any other front-end that implements the same scheme.
 
-*Version 3 supports only Rails 4+ and Ruby 2.3+. If you are still on Rails 3 (2, 1?!), you have to utilize version 2.1.1!*
+Check [version compatibility](https://github.com/jsanders/angular_rails_csrf/wiki/Version-Compatability) to learn which Rails/Rubies are currently supported.
 
 ## Installation