ZooKeeper 3.6.3 release.

[maven-release-plugin] copy for tag release-3.6.3-2

[maven-release-plugin] copy for tag release-3.6.3-1

[maven-release-plugin] copy for tag release-3.6.3-0

ZooKeeper 3.7.0 release.

[maven-release-plugin] copy for tag release-3.7.0-2

[maven-release-plugin] copy for tag release-3.7.0-1

[maven-release-plugin] copy for tag release-3.7.0-0

ZooKeeper 3.5.9 release.

ZooKeeper 3.5.9-rc2 release.