Simplifies the device manager code as we don't have to duplicate the
IP/network matching logic there.

Panic on short reads and other errors.

Which would be the GeoLite2-Country.mmdb one.

This enables correct (hopefully) support for IPv6 lookups. Also add
support for the special "onion" zone for Tor Hidden Services.

Otherwise gopkg.in/yaml.v2 won't decode strings to []bytes.