v0.3.0

This release contains some API cleanups - check for breaking changes.

☢️ Breaking changes

• timeout has been removed from the methods on the async Client. It is recommended to instead use asyncio.wait_for or similar to apply a timeout consistently across the entire task, which will allow it to apply if you use middleware that does I/O

📈 Enhancements

• WSGITransport now uses a shared module-level threadpool by default instead of creating one per instance. We imagine instances to be created commonly in tests and it is too tedious to deal with threadpools in them.
• HTTPHeaderName enum has been added both to provide type-safety when operating on headers but also a small performance improvement thanks to the memoization. str is accept in all places with it and this will never change.
• Some performance improvements by memoizing http method strings and status ints

Full Changelog: v0.2.0...v0.3.0