code: function(callback) {
          var headers     = this._formatHeaders(this.headers, this.params);
          if (this.payload != null) {
              headers['content-length'] = new Buffer(this.payload).length;
          } else if (this.method == 'POST' || this.method == 'DELETE' || this.method == 'PUT') {
              headers['content-length'] = 0;
          }
          var client = this.httpClient.http;
          if (this.scheme == 'https') client = this.httpClient.https;
          var httpRequest = client.request({port    : this.port,
                                            host    : this.host,
                                            method  : this.method,
                                            path    : this.uri,
                                            headers : headers},
                                           function(response) {
                                               var data = "";
                                               response.on('data', function(chunk) {
                                                   data += chunk;
                                               });
                                               response.on('end', function() {
                                                   var c = {
                                                       status  : response.statusCode,
                                                       headers : response.headers,
                                                       body    : data
                                                   };
                                                   callback(null, c);
                                               });
                                           });
          httpRequest.on('error', function(e) {
              callback(e, null);
          });
          if (this.payload !== null)
              httpRequest.write(this.payload);
          httpRequest.end();
      }
docs: Make request to the server
  Params:
  - callback