Bump docker-compose ZooKeeper version to 3.5.5 to fix compatability bug.

[jpittis]

Context

#605 describes a fatal issue with the existing docker-compose file that I resolved with the contents of this PR. Based on conversations in yahoo/CMAK#748, it sounds like Curator is no longer compatible with ZooKeeper 3.4.

How to reproduce and test

The following commands will reproduce the issue, which can then be resolved by using this commit instead:

$ mkdir mantis
$ cd mantis
$ wget https://raw.githubusercontent.com/Netflix/mantis/master/docker-compose.yml
$ docker-compose -f docker-compose.yml up

You'll likely need to prune your volumes when switching between versions to allow for the ZooKeeper upgrade.

Checklist

• ./gradlew build compiles code correctly
  • I'm unable to build Mantis as described in Errors building Mantis from source following official docs #604.
• Added new tests where applicable
• ./gradlew test passes all tests
  • I'm unable to build Mantis as described in Errors building Mantis from source following official docs #604.
• Extended README or added javadocs where applicable

[jpittis]

Closing as per #605. Helm should be used instead of docker-compose. We should update the docs to point to helm, and remove these outdated docker-compose files.