revise readme

tasks/cat_rename.wdl

@@ -13,7 +13,7 @@ task cat_rename {
 	runtime {
 		docker:docker
 		systemDisk:"cloud_ssd 40"
-		cluster_config:cluster_config
+		cluster:cluster_config
 		dataDisk:"cloud_ssd " + disk_size + " /cromwell_root/"
 	}