Use alternate method of logging deaths. Fixes #350

Is there any downside to this method?

http://jd.bukkit.org/rb/apidocs/org/bukkit/entity/Entity.html#getLastDamageCause() says "This event may have been cancelled" but presumably that's not the case if the entity died?

Not only should this fix #350 but since there's less processing, of an event that fires less often, it should have a (slight) performance increase, assuming there's no hidden caveats.