Update latest dependencies and address cors issue

* Update dependencies
* Update from tutorial
* Fixes this error using node cors:
  XMLHttpRequest cannot load http://localhost:3001/comments.json. The
  'Access-Control-Allow-Origin' header has a value 'http://localhost:3001'
  that is not equal to the supplied origin. Origin 'http://0.0.0.0:3000';
  is therefore not allowed access.

See http://stackoverflow.com/a/21622564/1009332
See http://en.wikipedia.org/wiki/Cross-origin_resource_sharing
That's what the cors module replaces, I'm guessing.