ELO calc method

/**
 * This method will calculate the change in a player's
 * Elo rating after playing a single game against another player.
 * The value K is the maximum change in rating. 
 **/
function calculateELORatingChange(elo1, elo2, k)
{
	var percentage = 1 / ( 1 + Math.pow( 10, (elo2 - elo1) / 400 ) );

	return {
		win: Math.round( k * ( 1 - percentage ) ),
		draw: Math.round( k * ( .5 - percentage ) ),
		loss: Math.round( k * ( 0 - percentage ) ),
		percent:  Math.round( percentage * 100 )
	};
}