Finish fixing up README.md.

Author: silug

README.md

@@ -1,7 +1,6 @@
-# sandbox
+# docker-sandbox
 
 This repo contains a Docker configuration for a basic CentOS 7 + Puppet AIO system
 suitable for demonstration purposes.  To use it, run the following:
 
-    docker pull puppetbootstrap/sandbox
-    docker exec -it sandbox /bin/bash
+    docker run --rm -it puppetbootstrap/sandbox /bin/bash