IPv6 support

[vtolstov]

Please add ipv6 support

[edaniels]

we could consider adopting some code from zeroconf which does a fair bit of this https://github.com/grandcat/zeroconf but it does have its own quirks.

[TA2k]

Do you have an update on this because in IPv4 mode no multiple mDNS server are possible in the same network

[edaniels]

There's some work in #173 that gets us a lot closer. Once that's in, I may just pick this up. This will need to ensure that we also are listening on IPv6 as well as sending to IPv6 multicast. There's a lot of references and the RFC for this (note to self: google around).