fix gnutar bailing out on Darwin as root group does not always exist
added --numeric-owner param if group is root on macos
Make debian control tarball use owner and group arguments.

Hardcoding --group=root in tar command breaks on OSX.

Fixes issue #429.
enable travis
Merge pull request #450 from AudaxHealthInc/fpm_fix_macos

Make debian control tarball use owner and group arguments (gnutar fix)