Added fadeout to gh-popover

Closes #2868
- Uses jQuery's `.fadeOut` whenever a popover is closed.

Death to the ancient issues!
Yeah, I tried playing that game before. It hurt.

open has a display:block important!;  ghost-popover has `display:none`.  if we had a fade-out class that used a fade-out animation, we'd have to turn off open after the fade out, which is what I'm doing already with jQuery