(Bug 5073) Tweaks, bugfixes, refactoring

* header-nav mixin has changed name and arguments. Also does a few more
  things, so remove redundant code

* bugfix: "underline" => underline. Strings with quotes around them are
  used as-is. So our CSS ends up having:

     text-decoration: "underline";

  Yuck.
(Bug 5073) Rename header-nav mixin to main-nav

Said mixin includes some code for vertical layouts as well
(Bug 5073) Add skiplinks to foundation in tropo

* use the skiplink components (tt block template, .scss file)
(Bug 5073) Tweak alignment for nav search

* aligns the search form elements with one another
* aligns the search form to match the rest of the top bar
(Bug 5073) Shrinks masthead/logo on tiny screens

Also shrinks the border strip of red in the header on tiny screens
(bug 2566) Auto expand text areas on the Suggest an Improvement page

Auto expands textareas on site/suggest.bml.
Merge pull request #45 from afuna/bug5073-tropo-adjustments

(Bug 5073) Tweaks to tropo (foundation version)
Merge pull request #44 from hotlevel4/bug2566/AutoExpandTextBoxesOnSuggest

(bug 2566) Auto expand text areas on the Suggest an Improvement page