Add ContextFactory (#25)

Author: barryvdh

composer.json

@@ -6,7 +6,7 @@
         {"name": "Mike van Riel", "email": "[email protected]"}
     ],
     "require": {
-        "php": ">=5.3.3"
+        "php": ">=7.1"
     },
     "autoload": {
         "psr-0": {"Barryvdh": ["src/"]}