- Fixed: ZooKeeper operations (including closing ZooKeeper
  connections) hung after network failures if ZooKeeper sessions were
  lost and ephemeral nodes (for registered services) had to be
  re-registered.

- Fixed: Didn't properly handle None values for node data returned by
  Kazoo 2.0.
be explicit about python versions
We introduced some threads, because it's not safe to make kazoo calls
in a session watch callback. So added sleeps to some of the tests
having to do with session recovery.
thread pain
Merge pull request #10 from zopefoundation/fixes-2014-08-27

Fixed, especially for hang on reconnect. (Don't know why travis shows as failing. The last runs there are green.)