Support SOA record type
pack_rdata_zone accepts dict, list, SOAType (namedtuple)
Merge branch 'master' of https://github.com/campadrenalin/pymads
Extend SOAType class with __str__
Record: add __str__ that returns RR's text representation
Test SOA record in test_packet and test_resolution
Test SOA: valid input types
Test SOA: frozen packet model
Close #37 : Merge in pczarn SOA record code