Add instruction to update docker-compose.yml when releasing new version (#471)

Author: longquanzheng

docker/README.md

@@ -65,3 +65,22 @@ docker run -e CASSANDRA_CONSISTENCY=Quorum \            -- Default cassandra con
     -e LOG_LEVEL=debug,info \                           -- Logging level
     ubercadence/server:<tag>
 ```
+Update docker-compose.yml when releasing new version
+=========================
+0. Creat new version tag in the repo
+1. Build the new docker image and push into docker hub
+```bash
+docker build . -t ubercadence/server:THE.LATEST.VERSION  --build-arg git_branch=vTHE.LATEST.VERSION 
+docker push ubercadence/server:master
+```
+2. Remember to update the docker-compose.yml to use latest version and check in to master
+```yaml
+  cadence:
+    image: ubercadence/server:THE.LATEST.VERSION 
+    ports
+```
+3. Create the tar.gz file and upload to relase page
+```bash
+cd github.com/uber/cadence/docker
+tar -cvf docker.tar.gz *
+```