Add Laravel 5.4 support.

Author: zachleigh

composer.json

@@ -12,11 +12,12 @@
     ],
 
     "require": {
-        "php": ">=5.6.0"
+        "php": ">=5.6.0",
+        "laravel/browser-kit-testing": "^1.0"
     },
 
     "require-dev": {
-        "laravel/laravel": "5.3.*",
+        "laravel/laravel": "5.4.*",
         "phpunit/phpunit": "~4.0"
     },