WeMOS D1 mini: hello world

Ref: https://github.com/wemos/D1_mini_Examples/blob/master/examples/01.Basics/HelloWorld/HelloWorld.ino

/*
 * Hello World
 * Simply prints Hello World to the serial monitor.
 */

void setup() {
  // initialize serial communications at 9600 bps
  Serial.begin(9600);
}

void loop() {
  Serial.println("Hello World.");
  delay(2000);
}