Mailcow: Adjust README for new repo structure.

The repository has been rewritten to base itself on git-subrepo rather
than git-subtree.  The README is updated accordingly.

Change-Id: Iecf45a46b8b1171e0764c6ee038889c0e5be90b6
1 file changed
tree: d08f17f096166a98f81429599d063f7b841ec3c3
  1. forks/
  2. mailcow/
  3. tikiwiki/
  4. images.nix
  5. makefile