Added support for passing dictionaries to KazooClient.__init__() in place of
KazooRetry objects. This feature was already outlined in the code documentation.

- Check if command_retry and connection_retry are dict before anything else
- Create KazooRetry from dicts before checking the sleep_func so that passing
  dict or KazooRetry ends up working the same.
- Added unit test for creating a KazooClient by passing a dict for both
  connection_retry and command_retry.
- Added assertion in client unit tests to ensure options passed as dictionaries
  to connection_retry and command_retry are set in the resulting objects.
Merge pull request #155 from ryanuber/kazoo_retry_dict

Allow passing dictionaries to KazooClient.__init__() for connection_retry and command_retry