Call for discussion: using Asciidoc instead of markdown for documentation

Hi,

this is something I had for a long time on my chest, but is getting more
and more on my nerves as I write more documentation, so I created an
issue for proper discussion:

https://github.com/rdiff-backup/rdiff-backup/issues/537

Honestly, if it would be only about me, I'd already have done the
conversion, so I expect solid arguments against the proposal, if someone
has them.

KR, Eric