Updated screenshot
resolving jquery ui css requesting missing images
Update CHANGELOG.txt
Added to wrong section previously
added Page.check exceptions for all parent classes

`Page.check` must be aware of all foreign keys which point
to parent classes. These keys are allowed to cascade on delete.
Merge pull request #796 from janrito/page_check_exception_squashed

added Page.check exceptions for all parent classes
Added @janrito to contributers
Changelog for #796
Create changelog / release notes section for 0.8.2