v0.2

Version 0.2 — Hashtables fixed and now linear probed

- Replace double hashing with linear probing for collision resolution
- Add tombstone marker to preserve probe chains after deletions
- Update set, get, remove, and delete logic to handle tombstones
- Add extensive tests for tombstone handling and probe chain correctness
- Update documentation to reflect new probing strategy and caveats
- Bump version to 0.2