Adds tabs, alerts, and breadcrumbs and makes small tweaks.

I'm pointing to my personal fork of cf-tabs for now because it's pretty nascent and I'm not exactly sure when it will officially get merged into the CFPB org. Same with cf-alerts and breadcrumbs. I also edited the grid and renamed it `.demo-grid` and made it responsive; the 1-3 column changes to 1-2 from 1023px to 768px and then changes to 1-1 under 768px.