Blood Artist's trigger ability is triggered for non-creatures

[gseitz]

During a test run, I destroyed an enchantment and Blood Artist's trigger ability was triggered, even though it should only be triggered when creatures die.

[MedeaMelana]

Right! Right now a trigger can't check yet if the object that moved to the graveyard was a creature so Blood Artist can't check yet whether it should trigger. We need to fix #26 first for this.