I want to install New Relic on one of my open source rails applications (v 3.2.12). I don't want to have the license key in the repo. I'd like to load it with something like ENV. 

By default that's loaded in the `newrelic.yml` file. 

Where is that YAML file loaded? I guess I could manually merge it with a hash that loads the license from the ENV hash.

Any hints on how to do that?