updated version to 5.2

Author: fabpot

composer.json

@@ -39,7 +39,7 @@
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {
-            "dev-master": "5.1-dev"
+            "dev-master": "5.2-dev"
         },
         "thanks": {
             "name": "phpunit/phpunit",