v1.7.3

Changelog

2d6c5cb Update client to fall-back to MD5 fingerprints
7d9a171 Use SHA256 hashes for key fingerprints
6ddc09d document udp, log client connection failures, expose more settings via env-vars
f04afd2 help goes to stdout and exits with 0, remove incorrect versioning from help
2092107 go dropped support for mips64p32, ppc, s390