<a> button :focus styles not overridden correctly.

Created by: LarryAzevedo

On any desktop browser, do the following:

1. Go to http://v4-alpha.getbootstrap.com/components/popovers/#dismiss-on-next-click
2. Click on the red Dismissible popover button to bring up the popover.
3. Finally, move your cursor off of the button.

The text of the button changes to blue; which in my opinion, looks and feels a little weird.