Added a toggle setting, updated demo to reflect the toggle, updated event listener syntax to jquery 1.9.0

I was unfamiliar with the document binding syntax that you were using.
$(document)[mousemove](zoom.move);

Is there benefit to this syntax that I'm missing out on by using jQuery's .on() or .bind/delegate/live methods? Or is it just an alternative syntax?

Great work, loved how easy it was to read and customize!