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* make sure keywords is in the assignment [martior]
* Make sure we load CMFCore (to avoid error on permission), fixes
http://plone.org/products/atsuccessstory/issues/5 [aclark]
* Make sure ATSuccessStory objects have a _tree attribute. This fixes
http://plone.org/products/atsuccessstory/issues/3 [esartor]
* Added categories field to portlet so it can filter by category [esartor]