Adds IPv6 support

* Contains all commits from #25, because ...
* ... only relevant if https://github.com/auraphp/Aura.Uri/pull/25 is merged (I wanted to do the work now, as a reminder to myself)
* If https://github.com/auraphp/Aura.Uri/pull/25 is merged, the only additional change is https://github.com/jeremykendall/Aura.Uri/commit/0857cc23f1f0d0b751c762b33d8cd72cbef1bfa6
* If #25 is not merged, I'll need to review what's needed to add IPv6 support.
* Based on https://github.com/jeremykendall/php-domain-parser/pull/35