Updated required PHP version

Author: jmsche

composer.json

@@ -25,7 +25,7 @@
     ],
     "minimum-stability": "dev",
     "require": {
-        "php": "~5.4",
+        "php": ">=5.4",
         "symfony/framework-bundle": ">=2.7",
         "leapt/core-bundle": "~1.0",
         "leapt/bootstrap-bundle": "v2.0.0-alpha.2",