* - encodecookies: bool, whether to urlencode the cookies (default: true)
* - resetcookies: bool, wheter to reset the cookies
* - cookiestore: string, path to a file where cookies are/will be stored
+ * - cookiesession: bool, accept (true) or reset (false) sessioncookies
* - resume: int, byte offset to start the download from;
* if the server supports ranges
* - maxfilesize: int, maximum file size that should be downloaded;
* - timeout: int, seconds the request may take
* - connecttimeout: int, seconds the connect may take
* - onprogress: mixed, progress callback
+ * - interface: string, outgoing network interface (ifname, ip or hostname)
+ * - portrange: array, 2 integers specifying outgoing portrange to try
* - ssl: array, with the following options:
* cert: string, path to certificate
* certtype: string, type of certificate