Have delayed_job recipe pass priority to the start script

Modify [default recipe](https://github.com/engineyard/ey-cloud-recipes/blob/master/cookbooks/delayed_job/recipes/default.rb#L35) to pass `min_priority` and `max_priority` when setting up monit's script.
In turn, also modify [monit's script](https://github.com/engineyard/ey-cloud-recipes/blob/master/cookbooks/delayed_job4/templates/default/dj.monitrc.erb#L3) to pass those values down the pipe. The [dj script](https://github.com/engineyard/ey-cloud-recipes/blob/master/cookbooks/delayed_job4/templates/default/dj.erb#L14) already knows how to handle priorities.