creating the tooltip element on the fly, never reusing it.
Use aria-describedby attribute to find the associated tooltip again.
Allows customizing animations much easier (just replace fadeIn/fadeOut),
still open.
Updated demos and visual test to replace now-missing .widget() method.
Added tooltipClass for that.
This reverts commit df31e22b95, reversing
changes made to ab8d155217.
Need to revert this revert later on when actually merging the tooltip branch into master.