[readme] Add branch to Coveralls URI

Author: Maks3w

README.md

@@ -1,7 +1,7 @@
 # zend-validator
 
 [![Build Status](https://secure.travis-ci.org/zendframework/zend-validator.svg?branch=master)](https://secure.travis-ci.org/zendframework/zend-validator)
-[![Coverage Status](https://coveralls.io/repos/zendframework/zend-validator/badge.svg?branch=master)](https://coveralls.io/r/zendframework/zend-validator)
+[![Coverage Status](https://coveralls.io/repos/zendframework/zend-validator/badge.svg?branch=master)](https://coveralls.io/r/zendframework/zend-validator?branch=master)
 
 The `Zend\Validator` component provides a set of commonly needed validators. It
 also provides a simple validator chaining mechanism by which multiple validators