1) Adjust the Announcer to cleanup parent nodes that it creates.  This stops it from leaving little turdlings lying around on zookeeper as nodes exit
2) Rename *CuratorDataSegmentAnnouncer because neither of them depend directly on Curator.
Merge pull request #195 from metamx/announcer-cleanup

Cleanup znodes left behind by announcer
Merge branch 'master' into batch-zk

Conflicts:
	client/src/main/java/com/metamx/druid/QueryableNode.java