[WIP] aura-todo update

So I wanted to take a closer look at Aura for a long time and thought updating the todo app would be a good start. I made some updates to the dependencies, Gruntfile, README and adopted the TodoMVC code style (w/o tabs so far) so it could be included at some point, but ran into some problems updating the actual integration with Aura as the API seems to have changed quite substantially since the app was written.

For example, in `extensions/aura-backbone.js` there's a call to `app.core.registerType` which no longer exists. @addyosmani Could you help me out there?