testing/httm: upgrade to 0.12.10

https://github.com/kimono-koans/httm/compare/0.12.8...0.12.10

- Update README.md
- Update README
- Better comments
- Cleanup main to be Config only
- Relative last in time snap paths
- Fix requested relative path to return correct path
- Better error
- Cargo fmt, clippy
- Bump version
- Include no-live as a conflict for last snap
- Add LastSnap to possible error
- Better comment
- Replace bare unwraps with expects
- Mark a few functions as private
- Remove some unneeded branches
- Remove unnecessary cloned()
- Bug fix re: deleted files not showing up
- Remove unnecessary clone by consuming iter
- Bump version
- Update Cargo.lock