Close tip popup on click outside the tip box.

Credit: http://stackoverflow.com/a/7385673/2867073
Only intercept <ESC> if we have an overlay shown
Stop propagation on intercept
Merge pull request #645 from protich/issue/close-tip-onclick

Close tip popup on click outside the tip box.

Reviewed-By: Jared Hancock <jared@osticket.com>