Prepare and check for Laravel 5.4. compatibility

Author: pixelpeter

composer.json

@@ -38,6 +38,7 @@
     "phpunit/phpunit": "^5.1",
     "mockery/mockery": "^0.9.4",
     "satooshi/php-coveralls": "^1.0",
-    "laravel/laravel": "5.2.*"
-  }
+    "laravel/laravel": "dev-develop"
+  },
+  "minimum-stability": "dev"
 }