Celery as a resource

So something really, really cool you can do with Poise is have it automatically handle this part for you. In the `Resource::Celery` class, you can do

```ruby
attribute(:init_file, cookbook_file: true, default_source: "celeryd", default_mode: 0755, default: lazy { "/etc/init.d/celery_#{new_resource.name}" })
```

and poise will automatically create the resource for you. Any attribute you would pass the resource you can add as an option to the attribute with `default_#{attribute}: value`, such as `default_mode: 0755`.