v0.6.0

What's Changed

• Lookup index #13. The db.lookup() can benefit from faster lookups with IPv4 index (an array of the first N bits of IPv4 addresses): it can skip the tree traversal for those bits. That can bring ~70%-140% speedup on sparse DBs and ~12%-18% on dense.
• db.open() and db.mmap() now receives Reader.Options that allows to build IPv4 index
• db.unmap() was removed in favor of db.close()
• Lookup cache #14, see lookupWithCache(). It showed ~15% faster GeoLite2-City.mmdb lookups on 1M random IPs (1.28M vs 1.47M lookups per second).
• within() was renamed to scan(), it doesn't cache anything internally. Now next() returns Result that needs to be freed with result.deinit()
• scanWithCache() was added to do network scans using a cache that owns the memory, i.e., no need to call result.deinit() though cache.deinit() is needed to free the cache

Full Changelog: v0.5.0...v0.6.0