Update Jedi to 0.16.0

[arshiyasolei]

https://github.com/davidhalter/jedi/releases/tag/v0.16.0

[karrtikr]

There are some big API changes associated with the new version. https://github.com/davidhalter/jedi/blob/master/CHANGELOG.rst#0160-2020-01-26

This may require some work.

[brettcannon]

Thank you for the suggestion! We have marked this issue as "needs decision" to make sure we have a conversation about your idea. We plan to leave this feature request open for at least a month to see how many 👍 votes the opening comment gets to help us make our decision.

We will need to discuss on the team the trade-off of all the great new features of this version of Jedi with its dropping of Python 2 support.