Align celerity/gradation-vertical/gradation-horizontal to the left

It looks weird otherwise (works in tropo because the menus are centered;
works in lynx because there are no menus)
Stop search from dropping below menu on smaller screen sizes

This is a bit of a hack:

* we shrink the search form + remove the down arrow on smaller screen
  sizes to reduce the horizontal space being taken up

* hopefully temporary: I'd like to revisit that search at some point
  (but that's for another bug)
Merge pull request #758 from afuna/tweak-foundation-from-feedback-round-4

Fourth round of changes from feedback