WIP: chore(build): Added serve task

- configured watch task to automatically reload server and rebuild assets
- server/index.js now exports the server object
- added bin/www to start the server directly (not sure how I feel about this)

@6a68 @pdehaan this still needs a few additions but is definitely ready for some feedback.

### TODO

- [x] Update README

Not sure if this `postinstall` should be modified as well here. I think I was being over-cautious and running `grunt build` after a `npm install`, but now that we're doing it in `npm start` it probably just adds an unnecessary compile.