public function html(array $options = [], array $namespaces = [])
    {
        $this->addNamespace('og', 'http://ogp.me/ns#');
        $this->addNamespace('fb', 'http://ogp.me/ns/fb#');

        if ($namespaces) {
            foreach ($namespaces as $ns => $url) {
                $this->addNamespace($ns, $url);
            }
        }

        $this->setType($this->config('type'));
        $this->setUri($this->request->here);
        $this->setTitle($this->_View->fetch('title'));

        if ($appId = $this->config('app_id')) {
            $this->setAppId($appId);
        }

        return $this->Html->tag('html', null, $this->config('namespaces') + $options);
    }