Kesslergame

- Added pause functionality for gamepad controller
- Added small dead zones to joystick and trigger inputs from gamepad controller for better human playability

- Fixed bug in ship-ship collisions where deaths were not properly counted for both ships.

- Fixed bug in relative imports of `GamepadController` class
- Updated `__init__.py` in `src` with `GamepadController`

- Fixed bug with `out_of_bullets` stop condition not covering all cases
- Fixed bug in `GraphicsTK` when `ui_settings` are `None`
- Added gamepad functionality for human players. To do so import `GamepadController` from `src.kesslergame.
controller_gamepad` and use when passing to game object just like `KesslerController`. Requires a Windows
compatible controller such as a wired X360 controller.

- Fixed bug where controller thrust and turn rate commands were not clamped to allowable range before being applied.
- Fixed bug where perferormance metrics were not returned after using `KesslerGame.run()`
- Added finalized controller references to `Score` object returned from `KesslerGame.run()`. Allows user to access saved characteristics of controller after simulation.

- Fixed bug in 1.3.0 where sprites used in Tkinter graphics would not be packaged into release wheel
- Added `KesslerGraphics` class to allow for the creation of custom graphics display interfaces