Fixed user model binding in Laravel 5.2

- The `class_uses_recursive` method only accepts objecs in Laravel 5.3 or greater. Laravel 5.2 only has support for strings.
- Closes #705

Author: stevebauman

src/Listeners/BindsLdapUserModel.php

@@ -52,6 +52,6 @@ protected function isUsingAdldapProvider() : bool
      */
     protected function canBind(Authenticatable $user) : bool
     {
-        return array_key_exists(HasLdapUser::class, class_uses_recursive($user));
+        return array_key_exists(HasLdapUser::class, class_uses_recursive(get_class($user)));
     }
 }