Add an Elasticsearch client

This patch adds a client. The client will be responsible to push new
indexes and new templates to Elasticsearch.
diff --git a/README.rst b/README.rst
index 7e9ccce..1d85c54 100644
--- a/README.rst
+++ b/README.rst
@@ -119,6 +119,20 @@
                   unit: days
                   unit_count: 2
 
+Client setup
+------------
+
+Client with host and port
+
+.. code-block:: yaml
+
+    elasticsearch:
+      client:
+        enabled: true
+        server:
+          host: elasticsearch.host
+          port: 9200
+
 Read more
 =========