[es] Include docker stack deploy instructions

For #124

elasticsearch/Dockerfile

@@ -4,7 +4,7 @@ MAINTAINER itzg
 
 RUN apk -U add bash
 
-ENV ES_VERSION=5.1.2
+ENV ES_VERSION=5.2.0
 
 ADD https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-$ES_VERSION.tar.gz /tmp/es.tgz
 RUN cd /usr/share && \

elasticsearch/README.md

@@ -1,5 +1,10 @@
 This Docker image provides an easily configurable Elasticsearch node. Via port mappings, it is easy to create an arbitrarily sized cluster of nodes. As long as the versions match, you can mix-and-match "real" Elasticsearch nodes with container-ized ones.
 
+# NOTE for use on Linux hosts
+
+Elasticsearch 5.x requires that the virtual memory mmap count is set sufficiently for stable,
+production use. [Refer to this guide for more information](https://www.elastic.co/guide/en/elasticsearch/reference/current/vm-max-map-count.html).
+
 # Basic Usage
 
 To start an Elasticsearch data node that listens on the standard ports on your host's network interface:
@@ -49,6 +54,24 @@ and then check the cluster health, such as http://192.168.99.100:9200/_cluster/h
       "unassigned_shards" : 0
     }
 
+If you have a Docker Swarm cluster already initialized you can download this
+[docker-compose.yml](https://raw.githubusercontent.com/itzg/dockerfiles/master/elasticsearch/docker-compose.yml)
+and deploy a cluster using:
+
+    docker stack deploy -c docker-compose.yml es
+
+With a `docker service ls` you can confirm 1 master, 2 data, and 1 gateway nodes are running:
+
+```
+ID            NAME        MODE        REPLICAS  IMAGE
+9nwnno8hbqgk  es_kibana   replicated  1/1       kibana:latest
+f5x7nipwmvkr  es_gateway  replicated  1/1       es
+om8rly2yxylw  es_data     replicated  2/2       es
+tdvfilj370yn  es_master   replicated  1/1       es
+```
+
+As you can see, there is also a Kibana instance included and available at port 5601.
+
 # Configuration Summary
 
 ## Ports

elasticsearch/docker-compose.yml

@@ -0,0 +1,37 @@
+version: '3'
+
+services:
+  master:
+    image: itzg/elasticsearch
+    environment:
+      TYPE: MASTER
+      UNICAST_HOSTS: master
+      MIN_MASTERS: 1
+    deploy:
+      replicas: 1
+      update_config:
+        parallelism: 1
+  data:
+    image: itzg/elasticsearch
+    environment:
+      TYPE: DATA
+      UNICAST_HOSTS: master
+    deploy:
+      replicas: 2
+      update_config:
+        parallelism: 1
+        delay: 60s
+  gateway:
+    image: itzg/elasticsearch
+    ports:
+      - "9200:9200"
+      - "9300:9300"
+    environment:
+      TYPE: GATEWAY
+      UNICAST_HOSTS: master
+  kibana:
+    image: kibana
+    ports:
+      - "5601:5601"
+    environment:
+      ELASTICSEARCH_URL: http://gateway:9200