code: function () {
                  var self = this, bar = self.get('bar'), child = null;
                  util.each(bar.get('children'), function (c) {
                      if (c.get('selected')) {
                          child = c;
                          return false;
                      }
                      return undefined;
                  });
                  return child;
              }
docs: get selected tab instance
  @return {KISSY.Tabs.Tab}