time-difference

USAGE

	var firstDate = new Date('6/4/2016');
	var secondDate = new Date('6/3/2016');

	var diff = timeDiff.absoluteDifference(	firstDate, secondDate ); // diff = 1

	var firstDate = new Date('6/10/16');
	var secondDate = new Date('6/20/16');

	var diff = timeDiff.difference( firstDate, secondDate ); // diff = -10