Raised the phpunit required to ~4.4

assertArraySubset() wasn't introduced until 4.4

Author: duncan3dc

composer.json

@@ -13,7 +13,7 @@
         "symfony/console": "~2.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.1"
+        "phpunit/phpunit": "~4.4"
     },
     "autoload": {
         "psr-4": {