pull in todomvc

### Demo: http://todomvc.stephenplusplus.com

This is PR part 4/4.

1. - [ ] unbreak todomvc-api: https://github.com/tastejs/todomvc-api/pull/2
2. - [ ] todomvc publishes to npm: https://github.com/tastejs/todomvc/pull/1050
3. - [ ] angular app merges into todomvc: https://github.com/tastejs/todomvc/pull/1050
4. - [ ] gcloud-node-todos pulls in TodoMVC

oh, I see.

I kinda like having `/api` serve the api doc, wdyt?

Maybe the client could do a `HEAD`