0.7.0

• Rewrote block index, fixes skewed MVCC (versions of items that span multiple blocks) scenarios
• Remove heap allocation from read hot path
• Improved read performance when using Levelled compaction (#26)
• Dropped serde, serde_json, chrono, rand and fs_extra dependencies (#25)
• Changed remaining file formats (config.json, meta.json, levels.json) to be binary encoded, in preparation of a stable disk format in 1.0.0
• Simplified disk segment IDs to be u64
• Internal refactors
• Added more tests and benchmarks