Fix error on ie9 when rednering recurrence widget inside an overlay.

On ie9 jquery internal method `$.buildFragment` crashes when the `defer`
attribute is set. This method is used by `plone.app.querytools`.
Furthermore, on ie9 js-code loaded into an overlay seems to be executed twice,
the first time the current page's globals are not available.
Merge pull request #14 from plone/deif-ie9-widget-fix

Fix error on ie9 when rednering recurrence widget inside an overlay.