Add container around content

To keep from moving the html element, this is probably unnecessary in
the grand scheme of things.
Move navbar-cover to before the navbar.
Make navbar-cover transition long enough for touch

It seems like the only way around the touch persistence problem is
having a long enough delay on the cover element so the touch stays away
from any links on the page. It's dirty but that's what it looks like we
have to do. 350ms seems to work well and it's not too slow. Also slowed
down the left transition to make it more equal.