bumping version to 3.10.0 (pymc-devs#4309)

* bumping version to 3.10.0

* adding PR 4211 and 4260 to release notes

* typo

Fixed error message referencing non-existent file (pymc-devs#4039)

Co-authored-by: AlexAndorra <[email protected]>

Set-up 3.9.2 Release (pymc-devs#3982)

* Updated RELEASE NOTES
* Bumped version number

fix tarball generation as 3.9.1 release (pymc-devs#3970)

+ removes docs/* from the tarball to fix PyPI size limits (setup.py and MANIFEST.in)
+ updates the release notes with 3.9.0/3.9.1 sections
+ black applied to setup.py

Rename property name in NUTS to better reflect the computation

Version 3.8 (November 29, 2019)

Upgrade to 3.7

Upgrade to 3.7.rc1.

Add date to release notes and note on dropping python 2 support.

Update verison to 3.6.rc1.