Fixed icon-spinner in Chrome. Fixed Styleguide icon listing.

All other icons place themselves in the :before pseudo-element, but `icon-spinner` was using :after for some reason. This broke it in Chrome (though not any other browsers), and also led to a kludge being put in place in the styleguide to handle that issue. A kludge that also minorly screwed up the icon listing in every browser.

This patch fixes both of those problems.