Upgrade Lumberjack to v7

Author: Tom Mitchelmore

composer.json

@@ -2,7 +2,7 @@
     "name": "rareloop/lumberjack-validation",
     "require": {
         "rakit/validation": "^0.13.1",
-        "rareloop/lumberjack-core": "^5.0.0||^6.0.0"
+        "rareloop/lumberjack-core": "^5.0.0||^6.0.0||^7.0.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^6.0",