rename simulateGame -> verifyGame
add .ghci file

Use with 'cabal repl'.
savegames: use hex strings for rng state
Random: rndSample: refactor
Random: roll: add comment
goIfOk: refactor

No functional change.
gameLoop: handle empty command edge case

This handles the case where the user enters "" (Enter) as the very first
command; we now avoid calling `goIfOk` with an empty string argument.