Navigation & search updates

This simplifies and improves the hover states in the full navigation
and corrects the position of the search in the navigation bar at mobile
widths.
Navigation color updates

Replaced RGBa values with LESS functions.
Mobile navigation search placement fix

Corrects placement of search when navigation is open and "scrolling."
Header updates

New, flat, pixel-fitted “N” flag; stripe border replaced with solid
color; addresses social icons in #593
Update to social icon display in header

@kabel Addresses Issue #593
Shorten logo hover transition time

Changed transition time from 0.2s to 0.1s.
Re-synced my branch

Trying to get everything back on the same page.
Uncommented line to handle the navigation active state

As requested by @kabel
Repair navigation

@kabel: Restored closing bracket and margin-bottom for desktop white
space on open.
Added extra line at end of document
Merge pull request #652 from skoolbus39/RD-Updates

Navigation & search updates