The reason polymorphic broke was because it couldn't find some managers
anymore in the inheritance tree. Django 1.5 removes these and replaces
them with an `AbstractManagerDescriptor`. This patch restores those objects
the regular Django dumpdata command now automatically works correctly
for polymorphic models and all Django versions
(this is handled by PolymorphicModelBase now).
Testing for dumpdata has been added.
- added python2.4 compatibility. Contributed by Charles Leifer. Thanks!
- general reorganization of the code - there is no single polymorphic.py module anymore,
so d-p now needs to be installed as a regular Django app
- polymorphic.VERSION/get_version added
- version numbering started: V0.5 beta