Prepare release 0.10.9.7 (py4j#495)

- Prepare release 0.10.9.7 
- Fix changelog of release 0.10.9.6
- Refine `py4j-python/release_process.md`

Merge pull request py4j#494 from xinrong-meng/release

Prepare release 0.10.9.6

Prepareing 0.10.9.5 release

Preparing for 0.10.4 release

preparing for 0.10.9.3 release (fixed graadle file)

preparing for release 0.10.9.2

preparing for release 0.10.9.1

preparing for release 0.10.9

Version 0.10.8.1 because I forgot python 3.7 in setup.py.

fixes py4j#333 - support for python 3.7 and preparing for release 0.10.8