Added some notes to the mixins design doc.
Somehow I missed fixing this issue of the selector not being populated in Chrome, just for this example.
Stating with the index of 0 is all we need to do here.
Factored out the event mechanism from the Uize.Class module and made it available in the new lightweight Uize.Event.Bus module. Also refactored the Uize.Node module to now use this smaller Uize.Event.Bus module for the window event vehicle in order to reduce the total size of the Uize.Node module when used outside of the context of widgets.