Added codecov tests coverage report

Author: vgarvardt

.travis.yml

@@ -10,4 +10,7 @@ script:
   - vendor/bin/phpunit
   - rm -rf vendor
   - composer update --prefer-lowest -n
-  - vendor/bin/phpunit
+  - vendor/bin/phpunit --coverage-clover=coverage.xml
+
+after_success:
+  - if [ "$TRAVIS_SECURE_ENV_VARS" == "true" ]; then bash <(curl -s https://codecov.io/bash); fi

README.md

@@ -7,7 +7,7 @@
 # hellofresh/stats-php
 
 [![Build Status](https://travis-ci.org/hellofresh/stats-php.svg?branch=master)](https://travis-ci.org/hellofresh/stats-php)
-[![Coverage Status](https://codecov.io/gh/hellofresh/stats-php/branch/master/graph/badge.svg)](https://codecov.io/gh/hellofresh/stats-php)
+[![codecov](https://codecov.io/gh/hellofresh/stats-php/branch/master/graph/badge.svg)](https://codecov.io/gh/hellofresh/stats-php)
 
 > Generic Stats library written in PHP