Update manifest

Fix paths for the manifest
Update setup.py package list

Only install the moderation package - the example project and tests don't need to be apart of the setup install.
Keep Moderation History

Add an option to GenericModerator that controls whether history of
 moderated objects should be kept or not.

Add a new "date_updated" field to ModeratedObject so that we can
 determine what the latest object is.

Update ModerationObjectManager.get_for_instance to try and get the
 moderated object the old way,.and if there are too many (because keep_history = True),
 find the most recent one and return that.

Add a test to make sure the post save handler works with keep_history

Add a test for ModeratedObjectManager to test get_for_instance