fixed startup command in readme

README.md

@@ -31,7 +31,7 @@ devoted to Docker. The demo seems to run well with 4 CPUs and 4GB.
 To run the demo:
 
 ```
-$ [TODO: INSERT DOCKER COMPOSE COMMAND HERE]
+$ docker-compose up
 ```
 
 You can log into the Grouper UI with "banderson/password". The account is a sysadmin. Also available is "jsmith/password", which has no explicit privs. There are lots of "user" accounts that have dumby course memberships.