fix php version, fix #6

Author: dpolac

composer.json

@@ -21,7 +21,7 @@
         }
     ],
     "require": {
-        "php": "^5.4 || ^7.0",
+        "php": "^5.6 || ^7.0",
         "twig/twig": "^1.0 || ^2.0",
         "dpolac/dictionary": "^1.0"
     },