0.3.1

version 0.3.1

Changes since 0.3.0:

• The experimental C implementation has been bumped to v0.0.1. Testers
  and reviewers can install this implementation from TestPyPI with:
  pip install -i https://test.pypi.org/simple/ blake3-experimental-c
• We now avoid releasing the GIL for short inputs and release the GIL
  for long outputs in addition to long inputs.
• The experimental C implementation now has GIL handling matching the
  Rust implementation.
• Both implementations now contain an internal mutex, to protect the
  state object from data races. However, it's still possible for data
  races to occur in the input buffer. (This is also the case for
  standard hashlib implementations.)