lib/twimap.js
function get_new_followers(since, cb, cberr) {
    get_inbox(since);
    _callback = cb;
    _callback_err = cberr;
}
function get_new_followers(since, cb, cberr) {
    get_inbox(since);
    _callback = cb;
    _callback_err = cberr;
}
function get_new_followers ( since , cb , cberr ) { get_inbox ( since ) ; _callback = cb ; _callback_err = cberr ; }
returns followers asynchronously

@param since date from which to look for followers e-mails
@param cb callback function when there is a result
@param cberr callback function on error
returns followers asynchronously