Jn/countdown

Countdown: Added countdown command.

* !countdown <time> <task>
* Countdown timer from 'n' (time in minutes set by user) to 0 for a task (text set by user).

Signed-off-by: Jakub Novak <jakub.novak@gmail.com>
Ah, OK, this is quite a misconception created by me, sorry for that.

The point of adding docstrings was to add docs to commands (decorated by @cmd). The user cannot really need docs for anything else. This class is kind of an example of it -- there is really no reason any user would like to see this docstring (however, as someone who is in charge of maintaining it I'd definitly prefer to have some there).

Again, sorry for that confusion I've managed to create.