function request(RequestConstructor, method, url) {
  // callback
  if ('function' == typeof url) {
    return new RequestConstructor('GET', method).end(url);
  }

  // url first
  if (2 == arguments.length) {
    return new RequestConstructor('GET', method);
  }

  return new RequestConstructor(method, url);
}
Issue a request:

Examples:

   request('GET', '/users').end(callback)
   request('/users').end(callback)
   request('/users', callback)

@param {String} method
@param {String|Function} url or callback
@return {Request}
@api public