Bump php require to 5.6, fixes #646

composer.json

@@ -24,7 +24,7 @@
         "classmap": [ "app/AppKernel.php", "app/AppCache.php" ]
     },
     "require": {
-        "php": ">=5.5",
+        "php": ">=5.6",
         "symfony/symfony": "^2.8",
         "doctrine/orm": "^2.4",
         "doctrine/doctrine-bundle": "^1.2",