Massive refactoring in a single commit. Sorry!

Grunt now builds from `src/*.coffee` to `bin/*.js`,
then browserifies and uglifies client-necessary scripts.

`class GameState` is now used throughout the app to
represent the state of a go board, instead of randomly
using `Array`s in some places.

This module now exports express middleware in
`src/express.coffee`. My goal is to eventually make it
modular enough that anyone who wanted to run URIgo could
`npm install urigo` then slap it into their express stack
with no more trouble than that.
Merge branch 'master' of https://github.com/bkietz/urigo
Adding simple turn tracking