Some minor changes

Hi Ben!

1) I extracted the loop iterating over all the canvases and creating nxObjects from them, and put it in a method `Manager.createNxObject`, so that it can be used to create nxObjects dynamically more easily.

2) I removed your custom event handler because it's simpler to just use node's builtin one :  http://nodejs.org/api/events.html#events_class_events_eventemitter it's very powerful, and it is less maintenance work since it is already done.