/**
 * Toggle class of Element between a & b.
 * Implemented into Element.
 * @var string|element el
 * @var string a
 * @var string b
 */
Element.implement({
	switchClass: function(a, b){
		if (this.hasClass(a)) this.addClass(b).removeClass(a);
		else this.addClass(a).removeClass(b);
	}
});