Changelog for release 5.3.0

[willingc]

Going under the assumption (based on early messages back on #452), we should start a changelog entry for the docs.

Edit this message with bullets.

New

• Multiprocessing and Threading support added Avoid kernel failures with multiple processes #437 and Backport #448 5.x zmq context isolation #450
• Setup package long_description added add long_description to setup.py #411

Changed

• Control channel now in the public API Exposes control channel in public API #447
• Closing Jupyter Client is now faster Make closing jupyter client faster #420
• Pip support improvements upgrade pytest #421

Removed

• Support for Python 3.3 and 3.4 dropped (upstream packages dropped support already)

Notes about installation or upgrade (if any)

The largest changes in 5.3.0 are the removal of older python 3 version support and the thread / process safe improvements to jupyter client. The latter change involved changing the zmq context objects to not be shared globally. The impact of this is that there will be a couple more C++ io threads running to handle messages along with some minor memory overhead. Overall these costs should be low compared to other adjacent costs and gives a much safer execution pattern. A big thanks to @alexrudy for digging in and finding the root problem here during PyCon's code sprint!

[SylvainCorlay]

Thanks @MSeal for editing the issue. This looks perfect.

Sorry for not tackling this earlier. We were in the rush to upgrade all possible extensions to JupyterLab 1.0 before Scipy - and a trip to the UK in the beginning of the week.

[MSeal]

No worries. I was also unavailable for a bit there.