refactor: move "No direct script access allowed" check below the header comment

Author: kenjis

libraries/Twig.php

@@ -1,5 +1,4 @@
 <?php
-defined('BASEPATH') or exit('No direct script access allowed');
 /**
  * Part of CodeIgniter Simple and Secure Twig
  *
@@ -8,6 +7,7 @@
  * @copyright  2015 Kenji Suzuki
  * @link       https://github.com/kenjis/codeigniter-ss-twig
  */
+defined('BASEPATH') OR exit('No direct script access allowed');
 
 // If you don't use Composer, uncomment below
 /*