Add a test for throning a feast.

I added a (failing) test for the behavior when playing Throne Room on Feast. The Feast should get trashed after gaining two Duchies, but instead it is discarded. I checked with Debug.Trace, and the player's Throne Room and Feast go into his discard pile instead of the trash; it would be nice to show that somehow in the test output, but this is my first time working with tests in haskell and I don't know how.

The fix for this is that (a) cards must go into the play area when played, and only get discarded at the end of a turn, during the cleanup phase, and (b) the Feast must get trashed at some point.