Add first draft of ZookeeperConsumer

Still need to add #create_streams_by_filter, or perhaps incorporate it
in #create_streams as a `:filter` option. Not really sure about it
though, as it returns a list instead of a hash.
Split modules / classes from `lib/heller.rb` to separate files
Convert Longs to Integers in ZookeeperConsumer

Need to explicitly convert each `count` value to a java.lang.Integer due
to Fixnum actually being a Long (I suppose at least?).
Add ZookeeperConsumer#create_streams_by_filter

Decided on only supporting whitelist filters for now, as I don’t really
see the point in supporting blacklists (though I’m sure someone else
will), so until someone requests the functionality or submits a pull
request there will only be support for whitelists.
Fix incorrect tests for ZookeeperConsumer#create_streams

Didn’t actually test that Fixnum’s was explicitly converted to Java
integers.
Add simple integration tests for ZookeeperConsumer

Nothing fancy, just to make sure that things actually work.
Rename integration test file

Vanity commit, NBD.
Merge branch 'zookeeper-consumer'