update multi-node docs

Author: blacktop

docker-compose.yml

@@ -31,8 +31,8 @@ services:
   data:
     restart: unless-stopped
     image: blacktop/elasticsearch:x-pack
-    environment:
-      - ES_JAVA_OPTS=-Xms2g -Xmx2g
+    # environment:
+    #   - ES_JAVA_OPTS=-Xms2g -Xmx2g
     command: data
     links:
      - master:elastic-master

docs/mutil-node.md

@@ -8,3 +8,5 @@ $ docker-compose up -d && docker-compose scale data=3
 > **NOTE**
  * Nodes have [X-Pack](https://www.elastic.co/products/x-pack) Plugin (*30 day trial*) installed  
  * Assumes your **data.nodes** have at least 4GB of RAM.
+
+With X-Pack the default user/pass is **elastic/changeme**