Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/barryvdh/laravel-debugbar/src/Facade.php

@@ -7,6 +7,6 @@ class Facade extends \Illuminate\Support\Facades\Facade
      */
     protected static function getFacadeAccessor()
     {
-        return 'debugbar';
+        return LaravelDebugbar::class;
     }
 }