code: function request(url, using, fn, disk) {
    if ('function' === typeof using) {
      disk = fn;
      fn = using;
      using = null;
    }
  
    if (!using) {
      if (curl) using = 'curl';
      else if (wget) using = 'wget';
      else using = 'node';
    }
  
    debug('requesting '+ url +' using '+ using);
    request[using + ( disk ? 'd' : '')](url, fn);
  }
docs: Request a HTTP resource and return it's contents.
  
  @param {String} url The HTTPS URL that we need to fetch.
  @param {String} using Optionally force which fetch engine we should use.
  @param {Function} fn Completion callback.
  @param {Boolean} disk Store file to disk instead of streaming spawns.
  @api private