code: function (tab) {
                  var self = this, bar = self.get('bar'), body = self.get('body');
                  bar.set('selectedTab', tab);
                  body.set('selectedPanelIndex', util.indexOf(tab, bar.get('children')));
                  return this;
              }
docs: set tab as selected
  @param {KISSY.Tabs.Tab} tab
  @chainable