- Added support for Python 3.3.

- Replaced deprecated ``zope.interface.implements`` usage with equivalent
  ``zope.interface.implementer`` decorator.

- Dropped support for Python 2.4 and 2.5.

- Refactored tests not to rely on ``zope.app.testing`` anymore.

- Fixed a bug while accessing the parent of a preference group.
Preparing release 4.0.0a1
Back to development: 4.0.0a2