Copy gitignore from CodeIgniter

Author: kenjis

src/Installer.php

@@ -28,6 +28,7 @@ public static function postInstall(Event $event = null)
         mkdir(static::DOCROOT, 0755);
         copy('vendor/codeigniter/framework/index.php', static::DOCROOT . '/index.php');
         copy('dot.htaccess', static::DOCROOT . '/.htaccess');
+        copy('vendor/codeigniter/framework/.gitignore', '.gitignore');
 
         // Fix paths in index.php
         $file = static::DOCROOT . '/index.php';