Collect data from mailing lists

Some data may only be available in mailing list (possibly such as CentOS #65 )
We could craft a module to deal with the common cases such as mailman/pipermail, etc. archives.
See:
- https://www.gnu.org/software/mailman
- https://github.com/matthicksj/mailman-download
- https://mail.python.org/pipermail/mailman-users/2012-October/074208.html
- https://github.com/wesleyd/pipermail-archive-to-maildir