add upper plotly.py version constraint

[jonmmease]

We should do another release of plotly_express that specifies an upper version constraint of plotly <4.0.0a0. Because we're integrating plotly_express into plotly.py v4, it would be good to avoid having folks install both plotly_express and plotly>=4.0.0.

[nicolaskruchten]

yep, PR it in and I'll do the release ;)

[nicolaskruchten]

Actually, I thought the "final" version of plotly_express would just re-export all of plotly.express instead... ?

[jonmmease]

PR in #103.

Actually, I thought the "final" version of plotly_express would just re-export all of plotly.express instead... ?

I think we should do both. Release the constrained version now, then when plotly.py v4 comes out, release a skeleton plotly_express that only remaps plotly.express.