Using D1 mini to link to wifi AP and create webserver for user to turn manipulate Pin 4 LED ON/OFF state.
Requires: Adding arduino D1 mini support: In Arduino preference -> settings -> add Additional Boards Manager URLs: http://arduino.esp8266.com/versions/2.3.0/package_esp8266com_index.json In Tools -> Board type, chooose "WeMos D1 R2 & mini" to upload the code.