monkeypatch File with a safe_link and use it in maildir source
rename sup-sync-back to sup-sync-back-mbox
Merge #162: Move sup-sync-back to sup-sync-back-mbox
update history and readme with maildir-syncback details
use safe_link
don't save thread on updated signal
dont sync_back when saving thread in threadindexmode, update in correct order
Merge branch 'develop' into maildir-root
Merge branch 'maildir-root' into running