add support for Jupyter 3.3.2

[OrenBochman]

This extension won't install on Jupyter 3.3.2

[euigfdbguiwerin93]

I think the reason may be Tornado. I faced some "event loop crashed" problems running this plugin. Luckily, when I downgraded my Tornado via pip from 6.1.2 to 6.1.0, everything worked fine. Hope this helps.