Clean up bullet-types module.
Clean up coroutine module.
Remove unnecessary let form from events module.
Rename add-event to add-event-type in events module.
Use #:use-module in define-module form rather than use-modules form.
Refactor keycodes module.
Clean up scene module.
Add functions to set bullet system bounding box and bullet killable flag.
Update primitives module to use some renamed bullet setters.
Set bullet system bounding boxes.
Update demo.
Update demo.
Update TODO list.
Add a much needed off method to events module.
Move wait generic to within coroutine module.
Update demo.
Update TODO list.
Change bullet system to use frame-based update rather than time-based update.
Change game to use frame-based update rather than time-based update.
Change director module to use frame-based update.