Fixes loader call

Author: alexstandiford

bootstrap.php

@@ -9,6 +9,6 @@
 
 // Add this loader.
 Underpin::attach( 'setup', new Loader('admin_bar_menus', [
-'instance' => 'Underpin\Admin_Bar_Menu\Abstracts\Admin_Bar_Menu',
-'default' => 'Underpin\Admin_Bar_Menu\Factories\Admin_Bar_Menu_Instance',
+'abstraction_class' => 'Underpin\Admin_Bar_Menu\Abstracts\Admin_Bar_Menu',
+'default_factory'  => 'Underpin\Admin_Bar_Menu\Factories\Admin_Bar_Menu_Instance',
 ] ) );