Use a specific version of phpunit-code-coverage

phpunit code coverage has a 2.x branch now with a different API

Author: dawehner

composer.json

@@ -9,7 +9,7 @@
         }
     ],
     "require": {
-        "phpunit/php-code-coverage": "*"
+        "phpunit/php-code-coverage": "1.2.*"
     },
     "require-dev": {
         "phpunit/phpunit": "3.7.*",