----------------
- Subclasses may now override existing methods (e.g. ``__setattr__``)
and use ``super`` to get at the overriden method.
- Transactions now see data in isolation.
- When a persistent object is first created, its state is immediately
local. This allows an ``__init__`` method to initialize the object.
- Added method to create a snapshot in time of an existing database.
- Added ``PersistentDict`` class.
- The ``Persistent`` class is now persisted as changesets rather than
complete object state.
- Set up tests to run using the nose testrunner (or using setuptools).