v4.0.0

Note that this release has been published on Sep 19, 2021 already.

What's Changed

• README: update links to the Open Patent Service (OPS) by @fe60 in #45
• Fix negative delays in sqlite middleware by @BeneCollyridam in #49
• Upgrade dependencies
• Drop support for Python 2.7 and Python 3.5
• Add support for Python 3.9

New Contributors

• @fe60 made their first contribution in #45
• @BeneCollyridam made their first contribution in #49

Full Changelog: v3.1.3...v4.0.0