fully support IPv6 connections and run the ezmq test suite for v4 and v6
fix validate_address for raw IP when DNS is not working

gethostbyaddr can fail with error nxdomain when DNS is
not working. Raw IP are ok even when DNS is not working
to cat the nxerror and only check the IP address in that case.
validate options before passing the to the socket process

This allows us to throw badarg errors instead of crashing the
socket process.
[RR-ony]: reduce travis test load and use travis badge for by repo