Diego Migration Issue

[lornajane]

As Bluemix moves to Diego, one of the changes is that the VCAP_APP_HOST environment variable (which was always set to 0.0.0.0) is no longer set. I notice we use VCAP_APP_HOST in this project, so this needs to be reviewed. For more info on the changes: https://github.com/cloudfoundry/diego-design-notes/blob/master/migrating-to-diego.md#cf-specific-environment-variables