Modify the cookbook to allow it to be run on any layer, not just 'rails-app'

[alexchumak]

It will restart the server in a rails-app layer only. And will only write
application.yml if it is a rails app that is being deployed.

Ran into this problem when created a utility instance that was running delayed jobs only and wasn't part of rails app layer. I needed to set env variables for the delayed job to work but application.yml wasn't being written because the instance wasn't part of rails-app layer.

[joeyAghion]

Sorry for the delay @alexchumak.

We use this cookbook for utility/worker instances as well, but we take a slightly different approach. The recipes are factored apart such that non-app server layers could implement their own custom recipe, analogous to the opsworks_custom_env::configure recipe, to define their own restart command and invoke the opsworks_custom_env::write_config recipe to write out the application.yml file.

In both cases, a custom cookbook is required. I think I prefer our approach, since the declarations end up in one location (rather than relying on a particular sequence of custom recipes being set for the layer).

Thoughts?