Hold Elasticsearch back on 2.4 for Chewy on macOS

So, Elasticsearch 5.0.0 is out. I’m using Chewy, a Ruby DSL gem that’s quite good. It’s not quite there yet with the deprecated Query APIs, (see Release Notes), so to keep using it you need to hold back to the Elasticsearch 2.4 series which is the last stable release. (Question about this, answered in the issue …