kibana documentation : environnement variable

The official doc does not mention that you can pass the address of you elastic search instance with the `ELASTICSEARCH_URL` environment variable.

See https://github.com/docker-library/kibana/blob/master/4.1/docker-entrypoint.sh

kibana/content.md

@@ -22,4 +22,8 @@ This image includes `EXPOSE 5601` ([default `port`](https://www.elastic.co/guide
 
 	docker run --name some-%%REPO%% --link some-elasticsearch:elasticsearch -p 5601:5601 -d %%REPO%%
 
+You can also provide the address of elasticsearch via `ELASTICSEARCH_URL` environnement variable:
+
+	docker run --name some-kibana -e ELASTICSEARCH_URL=http://some-elasticsearch:9200 -p 5601:5601 -d kibana
+
 Then, access it via `http://localhost:5601` or `http://host-ip:5601` in a browser.