Make the main `<nav>` element a TableObject
Make the main `<nav>` element a TableObject

There was a display issue, where navbar items's outline styles were
being cut off due to the parent `<nav>` element's margin and padding.

Fortunately, we can do away with the navbar wrapper div entirely. It was
not doing anything important except defining its children as
`TableObject` items. But we can just do this on the `<nav>` itself.

gollum/gollum,rgroux/gollum,gollum/gollum,repotag/gollum,repotag/gollum,rgroux/gollum,gollum/gollum,repotag/gollum,gollum/gollum,repotag/gollum,rgroux/gollum,rgroux/gollum,gollum/gollum,repotag/gollum,rgroux/gollum