Issue 340 - Nodejs page + TODO examples

https://github.com/rethinkdb/docs/pull/318 is a little messy because it's comparing to master.

There is one little issue left. `/docs/examples/node-todo-koa/` somehow shows a 404 page for me.
I'm pretty sure it was working before, and so far I still haven't found what's the problem (and if it's somehow that I need to fix in the markdown files, or if my Jekyll is broken).