0.18.3 and release notes

update release note date

0.18.1 and release note

0.18.0 release, release notes

0.17.3 release and notes

0.17.2 and release notes

expand cloudpickle range (openai#1836)

* expand cloudpickle range

* 0.17.1 release note

fix python_requires in setup.py (openai#1827)

version -> 0.15.7 (+revert api changes)

v0.16.0 release notes and version bump