@import font-awesome styles, instead of including

Currently the styles are included in stylesheets.

Properly import the font-awesome styles in our horizon.scss file,
so that we can set the variables and use the classes in our own
styles.

Change-Id: Ief1296d9c901ee4f6e6ebfdfa92347d5a8e4b9f1
Merge "@import font-awesome styles, instead of including"