myapp.HOST not working anymore after setting a custom domain

The README states that after setting custom domains for an app it will still respond to `myapp.HOST` in addition to the custom domains. The first is not true. The generated `nginx.conf` has this line:

    server_name www.superapp.com ssl.superapp.com

when it should have this:

    server_name superapp.HOST www.superapp.com ssl.superapp.com

I guess the plugin should also add `superapp.HOST` to the `hostname` variable?