5 tests passing for short break. Basic skip break behaviour implemented.
Can only skip a break when it's idle (i.e. after creation).
Moved short_break.py into production code folder.
Renamed ShortBreak class to Break.
Renamed short_break.py to rest_break.py.
Starting a break that's already started is an error.
Rearrange method order in Break class.
Break now calls back when time's up.
Break does not now call back _before_ time's up.
Changed refs to shortBreak to restBreak in tests.
RestBreak raises exceptions if stop is called when already skipped or
not running.
After stopping break no longer calls back.
After stopping, break is not running nor skipped.
Updated README with basic running instructions.