Changes in version 0.4.0:

Bugs fixed:
- Fixed a bug in the CI which sometimes made building beta executables fail.

New features:
- Snapshots now allow to use a label, to add a description and save the program version used.
- diff: diff can now compare snapshots with local dirs.
- backup: Added option --as-path.
- backup: Allow to use and save relative paths.
- backup: Added option --ignore-devid.
- backup: Now uses more parallelization.
- prune: Repacking is now parallel.
- New commands repair index/snapshots.
- Better support for using latest as snapshot.
- UI/progress bars: Added support for env variable RUSTIC_PROGRESS_INTERVALL.
- Simplified the code in some places.

Changes under the hood:
- rustic no longer uses async Rust.
- Replaced prettytables by comfytable. (Thanks @JMarkin)
