Load plotly.js from CDN rather than by inclusion

[baldwint]

Greatly reduces notebook file size by setting connected=True in the call to init_notebook_mode, as suggested here. Fixes #438.

[aggFTW]

Hey, thanks so much for sending this 👍

We have autovizwidget listing plotly version requirements here:
https://github.com/jupyter-incubator/sparkmagic/blob/master/autovizwidget/requirements.txt#L1
and here:
https://github.com/jupyter-incubator/sparkmagic/blob/master/autovizwidget/setup.py#L60

1.10.0 doesn't have that parameter available. It was introduced in 1.13.0. Could you please update the requirements there? I think it's good after that!

[baldwint]

Thank you for the review! And good catch. I modified the two files to update the minimum plotly version required.

[aggFTW]

LGTM. Waiting for @apetresc's feedback.

[apetresc]

Did some manual testing and everything seems to work fine 😄

That being said, I think it would be optimal to allow this to be configurable in ~/.sparkmagic/config.json, maybe with a key like embed_plotly - and I agree that connected=True (i.e, embed_plotly=False) should be the default value.

The tradeoff being made is that if we force connected=True, exported notebooks won't work at all if opened on a laptop without an internet connection, or on a particularly restrictive firewall, with no way to fix it.

I can make this change, just wanted to get @aggFTW's approval (on both the idea and the name of the key in config.json).

[aggFTW]

Yes, that sounds good! 👍 Will you merge then?

[thesuperzapper]

@apetresc @aggFTW is this going to be merged?

[thesuperzapper]

@baldwint