code: function quickReply(payload, callback)
  {
    if (typeof payload.payload != 'string')
    {
      payload.payload = JSON.stringify(payload.payload);
    }
  
    callback(null, payload);
  }
docs: Stringifies provided quick reply payload
  
  @this  Fbbot#
  @param {object} payload - quick_reply object
  @param {function} callback - invoked after stringification is done