set some got-dang visibility!

[miller-time]

currently (almost?) everything is pub... yeah, I was lazy.

possible steps forward:

1. remove all pub
2. cargo check
3. add pub(crate) as necessary
4. GOTO 2
5. play-test each level
6. add pub as necessary
7. GOTO 5

known items that must be pub:

1. top-level crate re-exports:

pub use actions::Direction;
pub use floor::Tile;
pub use game::Game;
pub use player::Player;
pub use unit::UnitType;
pub use warrior::Warrior;

2. all methods of warrior::Warrior

3. game::Game::play method