Add 3d glasses example demo

[danfinlay]

It's not perfect, but it's kinda neat, and would definitely help anyone else trying to make a better 3d-glasses-ready fox.

[kumavis]

createViewer needs an option to offset the model or camera

[danfinlay]

createViewer needs an option to offset the model or camera

Oh, that's a good idea, and would really help here. Should be easy enough to do, too.