initial minimax impl. and healing improvements.

main problem is that i have minimax coded incorrectly so bot decides to
go for the farthest away mine while passing many others on the way.
still works pretty well agains random bots, but gets smoked by real bots
better working minimax.  seems that the pathfinding breaks when passing
in coordinates sometimes.  May have something to do with the not exact
positions i supply.
updates to improve utility calculation and try to improve minmax
calcultion.  still sever bug
updates to tests and proper distance calculation
Merge branch 'minimax'

Conflicts:
	bot.py
	client.py
	game.py