Progress events for enyo.Async/enyo.Ajax

new enyo.Ajax/Async(...)
    .response(...)
    .error(...)
    .progress(function(inSender, inProgress) {
        //inProgress is something between 0 and 1
    })
    .go();

Custom enyo.Async kinds can implement their own progress functionality by calling this.setCurrentProgress(0...1);

As a default .go() sends the progress 0 and response()/error() send 1