ENH: Javascript mimetype and integrations

[TomAugspurger]

Just pass the the application/javascript mime types and document some integrations.

[jankatins]

And now comes the pain: knitr has the ability to include JS libs only once, but this isn't implemented in the jupyter messaging spec :-( It's a big painpoint as R has a lot of packages for html widgets which work nicely in knitr but blow up the size in the notebook as each displayed widgets needs to get all JS.

IRkernel/IRdisplay#14
-> jupyter/notebook#116 (comment)

[TomAugspurger]

I keep retreading all of your pain points :) Thanks for the links reading through them now.

[jankatins]

I think this is a painpoint more from the R (because they have a lot of such libs and are used to knitr's way of handling it, so no explicit activate which sends the js libs and then the rest doens't sent it) and jupyter side. I think this thing will be solved in one of the next versions... It's even worse in the notebook as they also save the output...