Bumping doctrine/common dependency to allow ^2.7.1

composer.json

@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": "^5.6 || ^7.0",
-        "doctrine/common": "~2.4"
+        "doctrine/common": "^2.7.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.4.6",