Geting JSON from ctx.payload.hits in a webhook action that Ruby consumes

Hey,

Just FYI: In Elasticsearch 2.4 and above we added a toJson mustache directive. See the PR https://github.com/elastic/elasticsearch/pull/19153 and the documentation of that one in particular https://github.com/elastic/elasticsearch/pull/19153/files#diff-b99a30a3f37550a69a2508b3a3e120a6R226

--Alex