code: function downloadFromUrl(page, ph, url, callback) {
      async.waterfall([
          function (callback) {
              page.getCookies(function (cookie) {
                  callback(null, page, ph, cookie);
              });
          },
          function (page, ph, cookies, callback) {
              var cookieString = helpers.cookieToHeader(cookies);
              var headers = { Cookie: cookieString };
              request.get({
                  url: url,
                  headers: headers,
                  encoding: null
              }, function (error, response, downloadedBytes) {
                  callback(error, page, ph, downloadedBytes);
              });
          }
      ], callback);
  }
docs: Downloads a file from a url
  @param page
  @param ph
  @param {string} url
  @param {pageResultCallback} callback