[FEATURE] add symfony 5 as possible dependency. and remove 2.x

Author: Simon Huebner

composer.json

@@ -10,7 +10,7 @@
         }
     ],
     "require": {
-        "symfony/framework-bundle": "~2.6||~3.0||~4.0",
+        "symfony/framework-bundle": "~3.0||~4.0||~5.0",
         "php-vcr/php-vcr": "^1.5"
     },
     "autoload": {