Add Hiera support

Allow configuration of the TLD and host ip address, via Hiera.

### Tasks
- [x] Update tests
- [ ] ~~Add `Debian.yaml` version~~

I'm not sure I am happy with this change. The convention for *all* boxen launchd services is `dev.{servicename}`. There's a lot of assumptions about that in tooling (e.g. running `boxen --list-services` looks for services named like that: https://github.com/boxen/boxen/blob/master/lib/boxen/service.rb#L13-L18 )