Move all frontend assets to a "public" directory

To prepare for the addition of a node backend, move all frontend assets
(js, html, css, hbs) to a "public" directory.
Get a koa node app serving the js app

Create a koa app that serves the static content for the js app. It also
has an endpoint to get a game collection which doesn't do anything yet
but will eventually be a json proxy for the bgg endpoint.
Use co-request to yield to a request to the api

Not actually working yet. Currently it's getting
their response but not setting my response.
Get the koa server working as a proxy for the bgg api

Since the bgg api doesn't support CORS, give this app the ability to
call the api server side.