function ReadableSerialOrdered(list, iterator, sortMethod, callback)
{
  if (!(this instanceof ReadableSerialOrdered))
  {
    return new ReadableSerialOrdered(list, iterator, sortMethod, callback);
  }

  // turn on object mode
  ReadableSerialOrdered.super_.call(this, {objectMode: true});

  this._start(serialOrdered, list, iterator, sortMethod, callback);
}
Streaming wrapper to `asynckit.serialOrdered`

@param   {array|object} list - array or object (named list) to iterate over
@param   {function} iterator - iterator to run
@param   {function} sortMethod - custom sort function
@param   {function} callback - invoked when all elements processed
@returns {stream.Readable#}