/**
 * Copyright (c) 2009 Sergiy Kovalchuk (serg472@gmail.com)
 * 
 * Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php)
 * and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses.
 *  
 * Following code is based on Element.mask() implementation from ExtJS framework (http://extjs.com/)
 *
 */