CURATOR-110 - Modified the CuratorFramework to expose a 'blockUntilConnected' method. This allows a race condition between the start() method and the ConnectionStateListener in the LeaderLatch recipe to be avoided. Updated the leader latch start() method to block until a connection is available (in a background thread), before it attempts to setup its state. This means that it will work correctly if started before a connection to ZK is available.