Add support to specify zookeeper root dir name

[bsara]

Currently, when using an external zookeeper instance, all data in zookeeper will be stored in /delta. There is no way to configure the name of this directory. Not only is delta a very generic name that could conflict with other services using the same zookeeper server, but it would just be nice to be able to specify what the root directory should be called for the user's convenience.

My particular scenario is that we have a dev environment and a test environment. Both of these environments share the same zookeeper servers. However, we want the data stored in zookeeper to be separate per environment for our rdf-delta server so that changes in one environment won't be expected to be applied to another environment. We already have different s3 buckets configured per environment, we just need the ability to change the name of something like the root directory used by rdf-delta in zookeeper and we will have everything working.

Having a way to define the root dir name via the cli would be ideal.

[bsara]

So, I'm quite new to zookeeper and didn't know about the ability to specify a directory in the connection string. I've used this to solve my issue.