[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?
I will document them.

`vars.yml` is for over-riding non vault values.

Specifying `secrets.vault` allows you to have local, non-encrypted overrides for `secrets.vault.yml`, but you can't commit them, which makes it handy for keeping them for easy inspection, etc.