Stripping cards from the Hand will also be useful, so I pulled the logic of Strip out into arrayutil (more efficiently, too) and rewrote deck.Strip to use it.
Given a function that identifies cards to remove, remove them from the deck. This can be used to find and strip out cards that are only conditionally appropriate (and aren't appropriate anymore).
Deck does enough stuff it should be its own thing; its internal representation might change to make multiple insertions not quadratic, among other reasons. Currently it just does the obvious stuff, though. Allows inserting cards in random or specific slots and drawing cards. Shuffling a range of the deck comes later.
