rustic 0.2.0-rc1

Version 0.2.0-rc1

This is the first release candidate for 0.2.0.

Changes in version 0.2.0:

• new commands: init, forget, prune, repoinfo, tag, key
• allow parallel lock-free repo access including prune
• added REST backend
• add compression support
• most operations are now parallelized (using async rust)
• added more statistical information to snapshots
• now uses the same JSON format for trees/nodes as restic
• better progress bars
• various small fixes