Update Persistent Data to use docker volume instead of data container (…

…sonatype#32)

* Update to creating Docker volume now that you can use docker volume to create a data container

* Update of text around commands

README.md

@@ -62,13 +62,13 @@ There are two general approaches to handling persistent storage requirements
 with Docker. See [Managing Data in Containers](https://docs.docker.com/userguide/dockervolumes/)
 for additional information.
 
- 1. *Use a data volume container*. Since data volumes are persistent
- until no containers use them, a container can created specifically for 
+ 1. *Use a data volume*. Since data volumes are persistent
+ until no containers use them, a volume can be created specifically for 
  this purpose. This is the recommended approach. 
 
  ```
- $ docker run -d --name nexus-data sonatype/nexus3 echo "data-only container for Nexus"
- $ docker run -d -p 8081:8081 --name nexus --volumes-from nexus-data sonatype/nexus3
+ $ docker volume create --name nexus-data
+ $ docker run -d -p 8081:8081 --name nexus -v nexus-data:/nexus-data sonatype/nexus3
  ```
 
  2. *Mount a host directory as the volume*. This is not portable, as it