Allow version 2 of the contracts package.

Author: derrabus

composer.json

@@ -17,8 +17,8 @@
     ],
     "require": {
         "php": "^7.1.3",
-        "symfony/event-dispatcher-contracts": "^1.1",
-        "symfony/service-contracts": "^1.1"
+        "symfony/event-dispatcher-contracts": "^1.1|^2",
+        "symfony/service-contracts": "^1.1|^2"
     },
     "require-dev": {
         "psr/container": "^1.0",