(option?) use CSS position: fixed whenever possible for navigation bars

[jokeyrhyme]

The scrolling area touch-event hack is necessary on iOS and Android<2.3, but many devices support CSS position: fixed.

In my own testing, web applications have much better performance characteristics for content in the scrolling pane. I've noticed that the web forms kitchen-sink widgets' animations are smoother when compared to the touch-event hacked technique.

This might be a solution to: https://github.com/davebalmer/jo/issues/22