Updated the phpunit dev version constraint

Author: GrahamCampbell

composer.json

@@ -29,7 +29,7 @@
         "sebastian/version": "~1.0.3"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.0.14",
+        "phpunit/phpunit": "~4.1",
         "ext-xdebug": ">=2.1.4"
     },
     "suggest": {