Update composer.json

Requires PHP >= 5.4.0

Author: Boy Baukema

composer.json

@@ -20,7 +20,7 @@
         }
     ],
     "require": {
-        "php": ">=5.3.2",
+        "php": ">=5.4.0",
         "symfony/framework-bundle": "~2.3|~3.0",
         "doctrine/doctrine-bundle": "~1.0",
         "doctrine/migrations": "~1.0"