Allow version 2 of the contracts package.

Author: derrabus

composer.json

@@ -18,7 +18,7 @@
     "require": {
         "php": "^7.1.3",
         "psr/container": "^1.0",
-        "symfony/service-contracts": "^1.1.6"
+        "symfony/service-contracts": "^1.1.6|^2"
     },
     "require-dev": {
         "symfony/yaml": "^3.4|^4.0|^5.0",