Import path, responsive CSS, minor fixes

+Changed import path to default Sync CSS. Changes to trim should be done at the theme configuration panel.

+Removal of responsive code from style.css and added to an override responsive.css to conform to SOP.

+Override for social-icons definition to allow our custom artwork. This is not ideal but consider this a first-version.

Signed-off-by: Glenn Batuyong <glenn@47ronin.com>