Policyd-rate-limit

Bugs fixes
- Yaml tuples are python list:
- For smtp server address and credential accept lists
- For SOCKET convert list to tuple when found
- Replace the parameter limited_netword by limited_networks (typo in the name)

Misc
- Use bages.genua.fr for badges
- Add a github version badges
- Add stacklevel to config warnings causing the warning to refer to config.setup()

Add yaml file to MANIFEST

Migrate configuration to a yaml file

If not config file found fallback to default config

- Continue running if asking for the value of a config param and we fail to drop privileges
- Do not leave **pycache** directory behind for the config file
- Add a publish_pypi_release target to Makefile to GPG sign releases

- Replace the module netaddr by the ipaddress available in the stdlib