This patch adds configuration to integrate with readthedocs.org, using
mkdocs as rendering engine.
It also does minor documentation updates, to tidy some things up
(clearer titles, move some documentation from the root into docs/, etc).
This patch contains some minor updates to docs/howto.md for simplicity
and readability.
In particular removing the "testing" qualifier from Debian, since the
guide can be used on Debian stable, and also removing a clarification in
a comment about a very old version of chasquid.
This patch adds a brief how-to guide for setting up an email server with
Debian, dovecot and chasquid.
It is incomplete, but has enough information that it's ok to include it.
