New SMS module for SIM800/900/etc

Hi!

Just an update to say that I've added a new module for SMS text messaging, to be found here: http://www.espruino.com/ATSMS

This works on most Espruino devices, and should work on most different types of GSM modem - but let me know if not!

For instance for Puck.js, I used D1 and D2:

// Connect to serial device
Serial1.setup(115200, { rx: D1, tx : D2 });
var ATSMS = require("ATSMS");
var sms = new ATSMS(Serial1);
//Use sms.at.debug(); here if you want debug messages

sms.init(function(err) {
  if (err) throw err;
  console.log("Initialised!");

  sms.list("ALL", function(err,list) {
    if (err) throw err;
    if (list.length)
      console.log(list);
    else
      console.log("No Messages");
  });

  // and to send a message: 
  //sms.send('+441234567890','Hello world!', callback)
});

sms.on('message', function() {
  console.log("Got a message!");
});

Note that using the serial port on Puck.js causes it to keep the oscillator on so it can receive serial data. This uses a bunch of power, so it'd be worth trying to power your Puck.js from the 3.3v regulator on your GSM module (which they usually have).