[WIP] Setting up a base new-relic setup using ansible vault

- Fixes #67 

This change also introduces a new `ansible-vault` secrets file, which has our encrypted `new-relic` key. A side-effect of this now you'll always need the vault key to deploy/setup.

Thoughts?
Also minor: might be good to add a comment here saying that this is automated instrumentation and so should be the very first thing in the file.

(Just so it doesn't get accidentally reordered, but also since it's unusual to have a `require` that isn't saved to a variable.)