README.md in embulk-output-elasticsearch-0.1.4 vs README.md in embulk-output-elasticsearch-0.1.5

@@ -8,9 +8,10 @@
 * **Cleanup supported**: no
 
 ## Configuration
 
 - **nodes**: list of nodes. nodes are pairs of host and port (list, required)
+- **cluster_name**: name of the cluster (string, default is "elasticsearch")
 - **index**: index name (string, required)
 - **index_type**: index type (string, required)
 - **id**: document id column (string, default is null)
 - **bulk_actions**: bulk_actions (int, default is 1000)
 - **concurrent_requests**: concurrent_requests (int, default is 5)