gut curses version, update README

Remove a lot of the stuff from the curses version that isn't needed for PXE,
but also quietly fix a few things:

* Fix lose conditions (well, remove them)
* Fix random picking to be resistant to poor PRNGs (like that used in coreboot!)
* Don't grant random blocks when a player makes a move that doesn't do anything

Also update the README with PXE-relevant information.