Add Test Coverage badge to README

Author: dannyvankooten

README.md

@@ -1,4 +1,4 @@
-# AltoRouter [![Build Status](https://api.travis-ci.org/dannyvankooten/AltoRouter.png)](http://travis-ci.org/dannyvankooten/AltoRouter) [![Latest Stable Version](https://poser.pugx.org/altorouter/altorouter/v/stable.svg)](https://packagist.org/packages/altorouter/altorouter) [![License](https://poser.pugx.org/altorouter/altorouter/license.svg)](https://packagist.org/packages/altorouter/altorouter) [![Code Climate](https://codeclimate.com/github/dannyvankooten/AltoRouter/badges/gpa.svg)](https://codeclimate.com/github/dannyvankooten/AltoRouter)
+# AltoRouter [![Build Status](https://api.travis-ci.org/dannyvankooten/AltoRouter.png)](http://travis-ci.org/dannyvankooten/AltoRouter) [![Latest Stable Version](https://poser.pugx.org/altorouter/altorouter/v/stable.svg)](https://packagist.org/packages/altorouter/altorouter) [![License](https://poser.pugx.org/altorouter/altorouter/license.svg)](https://packagist.org/packages/altorouter/altorouter) [![Code Climate](https://codeclimate.com/github/dannyvankooten/AltoRouter/badges/gpa.svg)](https://codeclimate.com/github/dannyvankooten/AltoRouter) [![Test Coverage](https://codeclimate.com/github/dannyvankooten/AltoRouter/badges/coverage.svg)](https://codeclimate.com/github/dannyvankooten/AltoRouter)
 AltoRouter is a small but powerful routing class for PHP 5.3+, heavily inspired by [klein.php](https://github.com/chriso/klein.php/).
 
 ```php