Buckshot-roulette

- Dealer rewritten and somewhat more performant. More importantly it should be closer to the real deal..
- `Items()` class can now be iterated over to see all items that you have more than 0 of.
- `charge_count` is now optional and can be randomly generated similarly to the actual game
- When the shotgun is reloaded, it now follows the correct shotgun bullet distribution (Before, the amount of live shells was independent of the total shells; this is incorrect as the amount of live shells = `total // 2`)
- Meds will no longer allow you to surpass the usual charge count maximum.

- Fixed the dealer, it doesn't completely fail to run now
- Proper abstract class for Engines
- Bugfixes to board
- `BuckshotRoulette.make_move` no longer returns the length of the shotgun unecessarily

- Dealer didn't set `self.me`
- Board __hash__() function used old dictionary syntax for Items

Initial Release! Mostly functional, I think!