public function download_file($id, $path) {
        $url = self::API."/${id}/content";
        // Microsoft live redirects to the real download location..
        $this->setopt(array('CURLOPT_FOLLOWLOCATION' => true, 'CURLOPT_MAXREDIRS' => 3));
        $content = $this->get($url);
        file_put_contents($path, $content);
        return array('path'=>$path, 'url'=>$url);
    }