Release 0.0.5

Remove PlayState finalizer and avoid creating Flash during cleanup.

The PlayState finalizer could call Dispose long after the PlayState had already
been cleaned up explicitly.

Also avoid touching Flash.Instance during PlayState cleanup. Disposing Flash did
not release anything useful, but accessing the singleton could lazily create it
for the first time during cleanup, at a point where the game may no longer be in
a valid state to load the flash effect.