Top nav bar style

Improved style overall to work with the hardware devices I tested it on (both Android and iPhone). It should look better on more devices now.

Also added some JS in `ApplicationView` for canceling scrolling on the body -- I know it looks somewhat janky, but 1) it works without any jumpiness, and works better than any pure CSS solution (especially for Android Chrome which is a real pain) and 2) apparently Facebook does something similar, as referenced [in this StackOverflow q/a](http://stackoverflow.com/questions/20230435/prevent-page-scrolling-to-top-upon-adding-fixed-position).

FYI the problem with what we had before with the `no-scroll` CSS class is that it was adding `position: fixed` to the body, which caused the page to jump to the top every time the menu was opened. But if we don't add `position: fixed`, then Android Chrome allows scrolling of the background, and the fixed overlay element jumps around horribly.
Em.