Sonic v1.7.0

This release was focused on making improvements to search results
(see Milestone #20 “v1.7.x - Better search results (non-breaking)”).
We benchmarked the changes, and concluded the performance impact of all those
changes is negligible. If you notice something now being noticeably slower,
please tell us as it might be a bug!

Changes

• Implement proper case folding (in f67f964)
• Rework QUERY results ranking algorithm (see Pull Request #355 “No implicit AND”)
• Logging improvements
• More tests

New Features

• Add support for diacritics-insensitive search (in 3d38caa, 2379b0a)
• Add support for stemming (in db83731)
• Introduce an official Rust client (in 5e1849d)
• bench: Introduce server benchmarks (in 8b9ec98)
• test: Introduce non-regression tests

Bug Fixes

• Fix max typo correction in QUERY (in 097a752)
• config: Fix non-string parsing from env (in b17daad)
• server: Fix buffer overflow detection code (in c85d97b)