Allow PHPStan 0.12

Author: simPod

composer.json

@@ -11,7 +11,7 @@
     ],
     "require": {
         "php": "^7.1",
-        "phpstan/phpstan": "^0.10 | ^0.11",
+        "phpstan/phpstan": "^0.10 | ^0.11 | ^0.12",
         "thecodingmachine/safe": "^0.1.11"
     },
     "require-dev": {