* sync with latest typeshed stub file (closes#54)
* publish `dev/mypy.allowlist` in sdist (closes#53)
* drop Python 3.7 support due to positional-only arg
syntax in the updated stub file
* Add Python 3.11 and 3.12 to CI (adjusting affected test cases)
* Add Python 3.11 and 3.12 to package metadata
* Drop Python 3.6 from package metadata
Note: typechecking is still disabled in CI for now
Closes#56
* use mypy.stubcheck to ensure stub API matches module API
* sync latest typeshed stub with nullcontext API fix
* use allowlist to ignore deliberately omitted deprecated APIs
Enabled back Travis CI testing in pypy3 env, using stable python 3.7
Updated setup.py according to all the changes
Fixed several formatting issues to better comply with PEP8