allow Laravel 6.0 (#9)

Author: Tom Schlick

composer.json

@@ -26,7 +26,7 @@
         "php": "^7.1",
         "awobaz/compoships": "^1.1",
         "fico7489/laravel-pivot": "^3.0.1",
-        "laravel/framework": "^5.8",
+        "laravel/framework": "^5.8 | ^6.0",
         "orisintel/laravel-process-stamps": "^1.2"
     },
     "require-dev": {