Resolved conflicts:
- VERSION: keep 0.6.0
- CHANGELOG.md: keep both 0.6.0 and 0.5.1 entries in order
- src/core/migrate.ts: renumber migrations (master's v2 slugify first, then v3 unique_chunk_index, v4 access_tokens)
- test/sync.test.ts: keep our test name ('normalizes to lowercase')