I use the following code, I have added the GW support for ESP board.
/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * DESCRIPTION
 *
 * Example sketch showing how to send in DS1820B OneWire temperature readings back to the controller
 * http://www.mysensors.org/build/temp
 */
// Enable debug prints to serial monitor
#define MY_DEBUG 
// Enable and select radio type attached
//#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69
// Use a bit lower baudrate for serial prints on ESP8266 than default in MyConfig.h
#define MY_BAUD_RATE 9600
#define MY_GATEWAY_ESP8266
#define MY_ESP8266_SSID "TP54C10"
#define MY_ESP8266_PASSWORD "blarretp54c10"
// The port to keep open on node server mode
#define MY_PORT 5003
// How many clients should be able to connect to this gateway (default 1)
#define MY_GATEWAY_MAX_CLIENTS 2
#include <ESP8266WiFi.h>
#include <SPI.h>
#include <MySensors.h>  
#include <DallasTemperature.h>
#include <OneWire.h>
#define COMPARE_TEMP 1 // Send temperature only if changed? 1 = Yes 0 = No
#define ONE_WIRE_BUS 3 // Pin where dallase sensor is connected 
#define MAX_ATTACHED_DS18B20 16
unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
DallasTemperature sensors(&oneWire); // Pass the oneWire reference to Dallas Temperature. 
float lastTemperature[MAX_ATTACHED_DS18B20];
int numSensors=0;
bool receivedConfig = false;
bool metric = true;
// Initialize temperature message
MyMessage msg(0,V_TEMP);
void before()
{
  // Startup up the OneWire library
  sensors.begin();
}
void setup()  
{ 
  // requestTemperatures() will not block current thread
  sensors.setWaitForConversion(false);
}
void presentation() {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Temperature Sensor", "1.1");
  // Fetch the number of attached temperature sensors  
  numSensors = sensors.getDeviceCount();
  // Present all sensors to controller
  for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {   
     present(i, S_TEMP);
  }
}
void loop()     
{     
  // Fetch temperatures from Dallas sensors
  sensors.requestTemperatures();
  // query conversion time and sleep until conversion completed
  int16_t conversionTime = sensors.millisToWaitForConversion(sensors.getResolution());
  // sleep() call can be replaced by wait() call if node need to process incoming messages (or if node is repeater)
  sleep(conversionTime);
  // Read temperatures and send them to controller 
  for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {
    // Fetch and round temperature to one decimal
    float temperature = static_cast<float>(static_cast<int>((getConfig().isMetric?sensors.getTempCByIndex(i):sensors.getTempFByIndex(i)) * 10.)) / 10.;
    // Only send data if temperature has changed and no error
    #if COMPARE_TEMP == 1
    if (lastTemperature[i] != temperature && temperature != -127.00 && temperature != 85.00) {
    #else
    if (temperature != -127.00 && temperature != 85.00) {
    #endif
      // Send in the new temperature
      send(msg.setSensor(i).set(temperature,1));
      // Save new temperatures for next compare
      lastTemperature[i]=temperature;
    }
  }
  sleep(SLEEP_TIME);
}
the exakt error I get in Arduino IDE is
In file included from C:\Users\xxxxx\Documents\Arduino\libraries\DallasTemperature/DallasTemperature.h:22:0,
                 from Z:\MySensors\NodeMCU-Water meter\NodeMCU-Water_meter\NodeMCU-Water_meter.ino:51:
C:\Users\xxxxxx\Documents\Arduino\libraries\OneWire/OneWire.h:108:2: error: #error "Please define I/O register types here"
 #error "Please define I/O register types here"
  ^
exit status 1
Error compiling for board NodeMCU 0.9 (ESP-12 Module).```