web todo: show tooltips for code

[michaelbjames]

Currently I assume the candidate code will come as a string, but Zheng and I agreed we'll send some kind of AST with type annotation for creating tooltips. I need to make some kind of code component that, given an annotated AST (in JS of course), will produce a DOM node with code and type tooltip highlights.

This doesn't rely on Redux, it's just about using React.

[peleghila]

I should have something we can cannibalize for that lying around. I'll dig it up.

[michaelbjames]

Eh, good enough for now? #110