Added backward-incompatibility note.
Fixed packaging bug.
- Renamed get_raw_properties back to get_properties, for
  backward compatibility, now that we've decided not to have a
  separate package.

- Added ensure_path to the testing client.

- Updated the ZooKeeper.close method to allow multiple calls.
  (Calls after the first have no effect.)
Merge branch 'kazoo' of github.com:zopefoundation/zc.zk into kazoo