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

I used it for `GET /api` and `GET /_ah/health`. It's not a big deal to inline.

The reason I used it for GET /api as well, is to give the FE apps a place to quickly ping to check for life.