Make MDNSService respond to questions for A/AAAA records about its hostname.
Update defaultTTL to 120 seconds.
Make mDNS server response more compatible with RFC 6762 spec.

- dns.Msg construction is now explicit, with comments pointing to the RFC about
  the values of each field.
- dns.Msg responses no longer contain a Question section, which is not allowed
  according to the spec.
- handleQuestion's interface returns both unicast and multicast answer records.
  (Note: These are not yet treated differently by the sendResponse method.)
- removed unused error return value of handleQuestion
Merge branch 'master' of github.com:armon/mdns into refactor-zone
Merge pull request #19 from gonzojive/default-ttl

Update defaultTTL to 120 seconds.
Switch to fork of go.net
Merge pull request #23 from ryanuber/fork-net

Switch to fork of go.net
Merge pull request #17 from gonzojive/refactor-zone

Refactor mdns.MDNSService API in zone.go.
Merge pull request #18 from gonzojive/hostname-questions

Make MDNSService respond to questions for A/AAAA records about its hostname.
Merge pull request #21 from gonzojive/handle-query

Make mDNS server response more compatible with RFC 6762 spec.
Fixing tests
Send response to multicast address if requested
Merge pull request #24 from brutella/multicast-response

Send response to multicast address if requested
Style cleanup
Respond to _services._dns-sd._udp.<domain> dns question
Add unit test
Merge pull request #26 from brutella/service-enum

Respond to _services._dns-sd._udp.<domain> dns query
Update README
Merge branch 'master' of github.com:hashicorp/mdns
Revert "Switch to fork of go.net"

This reverts commit d83f28beed4704edf65a99c470bd9112b8ac1684.