ghodss/yaml converts from YAML to JSON before attempting to unmarshal.
This allows us to:
* Get the correct behavor when decoding base64'd []byte slices.
* Use *json.RawMessage.
* Not have to support extravagant YAML features.
* Let our structs use `json:` tags
Allow users to define config values which are read form environemnt
variables. Helpful for sensitive variables such as OAuth2 client IDs
or LDAP credentials.