Improve infrastructure

- Adding a Makefile to centralize all the steps.
- Adding badges with current status.

You can check the README output here: https://github.com/magmax/python-repoman/tree/improve-infrastructure
This will only work in ubuntu-based distributions. I don't know if add-apt-repository is even installed by default in debian.
I'm not sure if I would put these dependencies in a so general rule, or even in the Makefile.