Merge branch 'es_install' into 'master'

Emphasize that ES is not included in the Omnibus packages

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/330

See merge request !226

doc/integration/elasticsearch.md

@@ -35,8 +35,10 @@ These are the minimum requirements needed for Elasticsearch to work:
 
 ## Install Elasticsearch
 
-Providing detailed information on installing Elasticsearch is out of the scope
-of this document.
+Elasticsearch is _not_ included in the Omnibus packages. You will have to
+install it yourself whether you are using the Omnibus package or installed
+GitLab from source. Providing detailed information on installing Elasticsearch
+is out of the scope of this document.
 
 You can follow the steps as described in the [official web site][install] or
 use the packages that are available for your OS.