require the needed symfony/contracts package

Author: xabbuh

composer.json

@@ -17,6 +17,7 @@
     ],
     "require": {
         "php": "^7.1.3",
+        "symfony/contracts": "^1.0",
         "twig/twig": "^1.35|^2.4.4"
     },
     "require-dev": {