Boustrophedon ordering

[tslumley]

If the error to be diffused over nearby hexes puts any of the triangles below zero, the negative part is passed on to the subsequent hex in rendering order. At the moment, the subsequent hex for a hex on the right edge of the plot is on the left edge. If we switched rendering order to go left to right along one row then right to left along the next, the error diffusion would be more accurate. Slightly.