code: function on(element, type, handler, opt, hook) {
      var types = type.split(' ');
      Utils.each(types, function(type) {
        Utils.on(element, type, handler, opt);
        hook && hook(type);
      });
    }
docs: simple event binder with a hook and support for multiple types
  @param {HTMLElement} element
  @param {String} type
  @param {Function} handler
  @param {Object} [opt]
  @param {Function} [hook]
  @param {Object} hook.type