Slight melee change

[MeowRailroad]

I just saw a colonist taking damage from an arctic fox's bite... when the fox was 4 cells away from the colonist. It looks really stupid and is also frustrating because you think, "Oh, the colonist is outrunning the fox... Wait, no, she's still being hurt by it." So i think it would be nice if melee could only work if they were touching, even while moving.