Install daemontools+runit on Ubuntu 12.04 because daemontools-run is broken on Ubuntu.
Set reasonable default values on resources, recreate scripts when their contents change and allow restarting upon changing script contents.
- The 'directory' attribute now defaults to #{service_dir}/#{service_name}.
- The 'template' attribute now defaults to service_name. It was already
  supposed to do that previously but it didn't work.
- Restarting upon changing script content is enabled through the
  'restart_on_change' attribute (defaults to true).