abbr[title] should not have border-bottom
Created by: Rewt0r
On the latest Firefox releases this is showing 2 underlines on abbr elements, the specification states that the default CSS for abbr[title] should be:
abbr[title], acronym[title] { text-decoration: dotted underline; }
Therefore this is not required in Bootstrap.
Refer to: http://www.w3.org/TR/html5/rendering.html#phrasing-content-0