Add Hiera support

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

I reckon we don't even need the `dnsmasq::config` class at all any more. A quick grep through the shared modules we use here at github shows nothing ever referencing it directly; it was only used internally in the `dnsmasq` module.