Add zookeeper service

[virtualdxs]

Per #20 add zookeeper service and set up a logs symlink since zookeeper seems to be ignoring the log4j.properties it's pointed at (I know little about this; I just know I was able to get Kafka running with my changes to this repo).

[id]

I'm sorry but I cannot accept this PR.
It will break many installations where zookeeper does not run on the same host as kafka. When kafka cluster grows beyond 3-5 nodes, having zookeepers running on the same machines becomes a headache.

[virtualdxs]

It shouldn't break those, as I used Wants instead of Requires. I can remove that and just have After so there's no dependency; would that resolve your concerns?

[id]

No, not really.
I still don't understand the reasoning behind this PR. If you need to install zookeeper, why can't you use separate package for this? https://github.com/id/zookeeper-el7-rpm

[id]

It's much easier to remove zookeeper scripts from this package and leave only zookeeper jar.

[virtualdxs]

That you'd have to ask the people who included Zookeeper in the Kafka tarball. Feel free to close the PR if you feel that the separate package is preferable.

[id]

Zookeeper library in kafka tarball is a necessity, just as any other third party library there.
But zookeeper shell scripts are not needed - I absolutely agree. The reason they are included in kafka tarball (my gueess) is that it makes it so much easier to quickly spin up kafka node on a local machine.
In production environments, however, an operator usually wants more granular level of control what package is installed where.