- Add a format string that uses text.Template. It's complex AF but it
works really nicely.
- Add a bunch of command line arguments to control the behaviour of the
countdown:
- Countdown duration
- Output format
- Output filename
- Text to write when done
- Fix countdown not starting until ~2 seconds after start.
- Replace unhelpful start up text with something a bit more useful
(parsed duration and output file name).