code: function RotaryEncoder(pinA, pinB) {
  	this.gpioA = new Gpio(pinA, 'in', 'both');
  	this.gpioB = new Gpio(pinB, 'in', 'both');
  
  	this.a = 2;
  	this.b = 2;
  
  	this.gpioA.watch((err, value) => {
  		if (err) {
  			this.emit('error', err);
  
  			return;
  		}
  
  		this.a = value;
  	});
  
  	this.gpioB.watch((err, value) => {
  		if (err) {
  			this.emit('error', err);
  
  			return;
  		}
  
  		this.b = value;
  
  		this.tick();
  	});
  }
docs: Creates a new Rotary Encoder using two GPIO pins
  Expects the pins to be configured as pull-up
  
  @param pinA GPIO # of the first pin
  @param pinB GPIO # of the second pin
  
  @returns EventEmitter