function del(url, data, fn) {
  const request_ = request('DELETE', url);
  if (typeof data === 'function') {
    fn = data;
    data = null;
  }

  if (data) request_.send(data);
  if (fn) request_.end(fn);
  return request_;
}
DELETE `url` with optional `data` and callback `fn(res)`.

@param {String} url
@param {Mixed} [data]
@param {Function} [fn]
@return {Request}
@api public