Removes rotunda icon from header. Gets smaller slab logo.
Prefetches some stuff. Adds app_name to site title. Adds Google Fonts css.
Adds classes for social media links. Removes duplicate vcard class.
More styling goodness.

* Adds social media icon font.
* Adds transitions for color, background-color, and opacity for links.
* Corrects some column widths.
Updates base variables.

Column and gutter widths are now calculated from the base line height instead
of arbitrary value.

Corrects padding on global header to better align with vertical rhythm.