added coveralls badge

Author: emsifa

README.md

@@ -2,6 +2,7 @@ Rakit Validation - PHP Standalone Validation Library
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 [![Build Status](https://img.shields.io/travis/rakit/validation.svg?style=flat-square)](https://travis-ci.org/rakit/validation)
+[![Coverage Status](https://coveralls.io/repos/github/rakit/validation/badge.svg?branch=setup_coveralls)](https://coveralls.io/github/rakit/validation?branch=setup_coveralls)
 [![License](http://img.shields.io/:license-mit-blue.svg?style=flat-square)](http://doge.mit-license.org)