WIP: Integrate client and server via Flux

Putting this up for discussion.

At present, this sets up a basic Flux architecture in the vein of https://github.com/facebook/flux/tree/master/examples/flux-todomvc and has the survey editor use it for saving.

The parts where it makes some XHRs to communicate with the server are still stubbed out, but I thought I'd put this up so we can work from it.

Thoughts?