libemu: Don't import 'sys.exit'
libemu: Re-allocate parent nodes on destroy()
libemu: Add require param to parse_snapshots()
libemu: Sync "Most Recent Backup" and HEAD
libemu: Fix head re-allocation in destroy()
emu: Add an 'emu prune' command
scripts: Add mkrelease.sh script
Bump release version for '0.1.3'
scripts/mkrelease: Push new tag and release commit
libemu: Support '!=' operator for SnapshotID
libemu: Use concurrency locks for destroy()
libemu: Add local convenience variable
libemu: Reword destroy() output
libemu: Add setter to Stack.head()
libemu: Refactor to use head()
libemu: Enforce proper --dry-run behaviour
Bump release version for '0.1.4'