Import the entirety of CFPB's design system (#105)

Instead of selectively importing Less rules based on the needs of
individual components, import the entire Less stylesheet.

src/assets/styles/_shared.less

@@ -1,5 +1,5 @@
 /*
  Shared styles, variables, and css overrides
 */
-@import (reference) '@cfpb/cfpb-design-system';
+@import '@cfpb/cfpb-design-system';
 @import './variables.less';