Returned support for PHP 5.5

composer.json

@@ -33,7 +33,7 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "~5.2",
+        "phpunit/phpunit": "~4.8",
         "squizlabs/php_codesniffer": "~2.5"
     }
 }