- Fix multipart parser for some files to prevent denial of service ([@aiomaster](https://github.com/aiomaster))

- Fix `Rack::Builder#use` with keyword arguments ([@kamipo](https://github.com/kamipo))

- Skip deflating in Rack::Deflater if Content-Length is 0 ([@jeremyevans](https://github.com/jeremyevans))

- Remove `SessionHash#transform_keys`, no longer needed ([@pavel](https://github.com/pavel))

- Add to_hash to wrap Hash and Session classes ([@oleh-demyanyuk](https://github.com/oleh-demyanyuk))

- Handle case where session id key is requested but missing ([@jeremyevans](https://github.com/jeremyevans))