Add Laravel 5.8 support (#103)

* Add Laravel 5.8 support

Author: tvbeek

composer.json

@@ -17,7 +17,7 @@
   ],
   "require": {
     "php": "^5.6 || ^7.0",
-    "illuminate/support": "5.3.* || 5.4.* || 5.5.* || 5.6.* || 5.7.*"
+    "illuminate/support": "5.3.* || 5.4.* || 5.5.* || 5.6.* || 5.7.* || 5.8.*"
   },
   "require-dev": {
     "phpunit/phpunit": "^5.7 || ^6.0",