Convert string references to ::class

PHP 5.5.9 adds the new static `class` property which provides the fully qualified class name. This is preferred over using strings for class names since the `class` property references are checked by PHP.

app/Conductors/UserConductor.php

@@ -10,7 +10,7 @@ class UserConductor extends Conductor
      * The Model Class
      * @var string
      */
-    protected $class = '\App\Models\User';
+    protected $class = \App\Models\User::class;
 
 
     /**