code: public static function flag($country, $options = [])
      {
          Ui::addCssClasses($options, ['flag', $country]);
          return Ui::tag('i', '', $options);
      }
docs: Renders a [flag](http://semantic-ui.com/elements/flag.html)
  
  @param string $country the flag's country ISO code to render
  @param array $options the tag options in terms of name-value pairs
  
  @return string the generated flag tag