Applications for this include compression and encryption.  An
  example wrapper storage implementation, ZODB.tests.hexstorage, was
  included for testing.

It is important that storage implementations not assume that
  storages contain pickles.  Renamed IStorageDB to IStorageWrapper and
  expanded it to provide methods for transforming and untransforming
  data records.  Storages implementations should use these methods to
  get pickle data from stored records.

- Deprecated ZODB.interfaces.StorageStopIteration.  Storage
  iterator implementations should just raise StopIteration, which
  means they can now be implemented as generators.