Make sure instance has user attribute, in case super.__init__ stringifies (logging, for example).
Require all kwargs to Chinup instantiation.
Chinup.callback applies only to first page.
Pass callback through ChinupBar().get() and friends.
Rewrite DEDUP to be fast, and run in sync() rather than append().
No need to compare callbacks with new DEDUP support, since duplicate chinups all get assigned the same response.
Pass migrations through ChinupBar to Chinup, so it can be set on a per-request basis rather than globally.
Add support for ?summary=true to get total number of records.