Merge pull request #3 from bolt/test/add-twig-dependency

requiring twig (for test)

Author: I-Valchev

composer.json

@@ -10,7 +10,8 @@
         }
     ],
     "require": {
-        "php": ">=7.1.3"
+        "php": ">=7.1.3",
+        "twig/twig": "^2.12"
     },
     "require-dev": {
         "bolt/core": "^4.0.0",