Merge pull request #36 from arnedesmedt/master

Allow psr container v2

Author: Alexander Miertsch

composer.json

@@ -25,7 +25,7 @@
     "event-engine/php-persistence": "^0.8 || ^0.9.1",
     "event-engine/php-schema": "^0.1 || ^0.2 || ^0.3",
     "fig/http-message-util": "^1.1",
-    "psr/container": "^1.0",
+    "psr/container": "^1.0 || ^2.0",
     "psr/http-message": "^1.0",
     "psr/http-server-middleware": "^1.0"
   },