maint: improve `domain`, `email` & `hostname` by nandgator · Pull Request #244 · python-validators/validators

@nandgator

- in `domain`: decode value to `utf-8` instead of `ascii`; use `re.match` directly
- in `email`: split `ip_address` to `ipv4` and `ipv6` parameters
- in `hostname`: split `skip_ip_addr` to skip `ipv4` & `ipv6` parameters