This is the simple app I put together as the demo for my talk at GOTO Aarhus 2012. To get to any "chapter" just checkout tag xN where N is 1 through 7. So to check out chapter 4:
% git checkout x4
To run it you'll need a recent version of node 0.8. I've been using n so installing is as simple as setting N_PREFIX and adding $N_PREFIX/bin to your path. Then you run:
% n 0.8.21
which will install and enable that version. (Try n list to see which versions are available.)