added hexagonal spread packing (in only one direction)

This makes both the unjiggled and jiggled score better in this case, although it might not often outdo best known or physical:

![screen shot 2014-11-10 at 2 09 08 am](https://cloud.githubusercontent.com/assets/2453460/4972676/ade7db04-68af-11e4-870c-3b6169dfd5bd.png)
![screen shot 2014-11-10 at 2 18 27 am](https://cloud.githubusercontent.com/assets/2453460/4972677/adee2bbc-68af-11e4-8d40-cf4eed61fcb5.png)