Gormlaks now move 1/8th the speed of the character, which means we can
run away from them - yay!
Unfortunately this also introduces a bug where they'll eventually get
stuck and not do anything, so I'll be tackling that next.
Previously the isUnit function was falsely returning `True` for
positions that were one tile off in *either* direction from the
character, when it should've been *both*. Oops.
When gormlaks see the character, they step towards them and attack
dealing 1 damage when adjacent. Characters have hitpoints now, displayed
at the bottom of the game screen, and when the game is over they die.
