Reopen - Suggested fix for #8740

Tooltip: Register event handlers before content is loaded. Fixes #8740 - Tooltip: Does not hide consistently with dynamically loaded content.

See http://bugs.jqueryui.com/ticket/8740

I don't really know whether creating a new pull-request is necessary or whether the old one (#973) could be re-opened. At least I haven't found a way to reopen the old one. If this would've been possible, let me know.