Zookeeper dependency broken on earlier versions.

[Inphi]

Older versions of node-zookeeper cannot build the zookeeper library. This is because it attempts to retrieve the zookeeper c client version 3.4.3 for building. For whatever reason, that version of the C client no longer exists in Apache mirrors. The maintainer of node-zookeeper has fixed this by publishing prereleases of zookeeper-3.4.6. However the fix is only available for [email protected]. Since it's infeasible to expect the node-zookeeper maintainer to retroactively patch all earlier versions, I think it'll be better to update node-zookeeper-explorer's dependency on node-zookeeper.

[radekg]

@Inphi I'll happily accept a pull request.