Remove podcasts I don't listen to, add new ones to try.

Trying some new podcasts.

I don't find any interesting content in those podcasts.

- Remove comments. They're from an old version and not very useful.
- Set default max_number.
- Set a restrictive filename policy. I needed it before for some
  podcasts but if I'm not sure why.

The usage is completely replaced. Now locally I run inside a pipenv and
remotely using Docker.

- Use Supersonic as the Cron daemon.
- Run locally using pipenv.
- Run remotely using Docker (and docker-compose).
- Automate tasks using pipenv custom script shortcuts.
- Updated pre-commit hooks, added yamllint hook.
- Added license.
- Updated README.