Look at if Yarn and Webpack can be used when Rails 5.1 is released

[jensljungblad]

Crazy idea, but Rails 5.1 will ship with Yarn and Webpack. What does that mean for gems? Could we build on top of that? What about React? Better datepickers and selectboxes would be available. Integrating with Rails could be troublesome though... How would view overriding work? Ties into #223.

This should also obviously be based on what type of design we decide to go with in #224. A richer interface would perhaps benefit from something like React while what we have now would not.