Fixes social icon wrapping on iPad.
Re-added IE8 polyfills. Added position-sticky polyfill.
Updated search images (using new brand grays).
Some polish on tablet/desktop header and footer.
Merge pull request #131 from DoSomething/nav-pass-two

Nav pass two
Release v3.0.5
Uses flexbox to expand footer to bottom of screen on small content heights.
Added hamburger icon to icon font.
Mobile nav in the header.
Icomoon mixin for use elsewhere.
Removed "is-hidden-on" classes.
Unrounded search fields.
Removed some lipsum from homepage template.
Made iPhone 5 media query into a variable.
Removed deprecated flex-width mixin.
Removed old pin-to-top code..
Removed last uses of old respond-to mixin.
Fixed errant link underline.
Added right and down arrow glyphs to icon font.
More traditional naming convention for retina assets.