Update composer.json

Author: nilportugues

composer.json

@@ -29,7 +29,7 @@
         "php": ">=5.5"
     },
     "require-dev": {
-        "phpunit/phpunit": "5.*",
+        "phpunit/phpunit": "4.*",
         "fabpot/php-cs-fixer": "~1.9",
         "nilportugues/php_backslasher": "~0.2"
     },