fix hitting back on nav, use more css over js for active styling (bug 1058996)

The behavior of the nav should remain the same. Except this fixes hitting "back" on desktop (i.e., there was duplicate pushStates, and hitting back didn't update the nav activness). Fixed by:

- remove duplicate navigation triggering
- defining the tab activeness in CSS using body[data-page-type] rather than CSS
I've already noticed the spacing is off in English. and we are an international marketplace. we cannot do it that way at all. you should file a bug to change this.

we can totally calculate the offsets and set the `right` property with just a few lines of JS, and it'll be accurate.