public function url($name, array $options = null)
    {
        $options = is_null($options) ? array() : $options;
        $group = $this->createGroup($name);

        $cache_buster = '';
        if (array_get($options, 'md5', $this->md5)) {
            $cache_buster = '?'.md5_file($this->file($name));
        }

        $secure = array_get($options, 'secure', $this->secure);

        return URL::asset($group->getTargetPath(), $secure).$cache_buster;
    }