Untabify
Archiving

Use C-c C-a (deft-archive-file) to archive a file
in deft-archive-directory.

Thanks to Alberto Ferrarini for the suggestion and a patch.
Update buffer visiting file when renaming or archiving
Improve, document, and autoload deft-find-file

Also, ensure that Deft is loaded before setting up auto save hooks.
Fix and improve docstrings
More robust and explicit handling of relative, absolute, and short filenames

Filenames are relative or absolute paths, slugs are short filenames
without paths or file extensions.
Display a short message when Deft is loading
Silence warnings about using cl functions at runtime