Bootstrap .caret to FontAwesome icon font caret

Per my conversations with @edmistj, we want to switch from Bootstraps default .caret to the FontAwesome .fa-caret-down

Bootstrap's version uses borders to make it's triangle shape — so you have to set border-color to get it to match the surrounding text.

Font Awesome's version is just an icon font, so it will automatically inherit text color, making everything much simpler.