use 4.0 from symfony

Author: ElectricMaxxx

composer.json

@@ -10,7 +10,7 @@
     ],
     "require": {
         "php": "^5.6|^7.0",
-        "symfony/symfony": "^2.8|^3.0",
+        "symfony/symfony": "^2.8|^3.0|^4.0",
         "symfony/phpunit-bridge": "^3.2",
         "symfony/monolog-bundle": "^2.1|^3.0",
         "doctrine/common": "^2.4",