Hapi mode

This pull request replaces `Express` with `Hapi` for the main application server. It sets up a proxy to `webpack-dev-server` so that assets have access to features such as hot module replacement.

Additionally, I changed the way actions are accessed, following some interview material with Facebook staff working on their flux apps.
This redirects traffic behind `/assets` to Webpack. I imagine we could use this same technique for proxying API requests, as described here:

https://gist.github.com/hueniverse/7686452

@ltk pretty cool, huh?