Allow Symfony 4 usage

Author: ScullWM

composer.json

@@ -12,9 +12,9 @@
     "require": {
         "php": ">=5.5.0",
         "psr/log": "~1.0",
-        "symfony/event-dispatcher": "~2.5|~3.0",
-        "symfony/serializer": "~2.5|~3.0",
-        "symfony/dependency-injection": "~2.5|3.0",
+        "symfony/event-dispatcher": "~2.5|~3.0|~4.0",
+        "symfony/serializer": "~2.5|~3.0|~4.0",
+        "symfony/dependency-injection": "~2.5|3.0|~4.0",
         "doctrine/inflector": "~1.0"
     },
     "autoload": {