Closes #109 Updates phpunit dependency

composer.json

@@ -30,7 +30,7 @@
         "symfony/finder": ">=2.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "3.7.*"
+        "phpunit/phpunit": ">=3.7"
     },
     "target-dir": "Mmoreram/GearmanBundle",
     "autoload": {