dns_update needs to run with bash when run directly, see #39
redirect all HTTP to HTTPS and enable HSTS, closes #18
add more postfix rules: reject_non_fqdn_sender, reject_unknown_sender_domain, reject_rhsbl_sender, and permit_dnswl_client
clean up README a bit; moving the bit Rationale into the github wiki
test_mail: if EHLO test fails continue testing the rest, since user may be waiting on DNS propagation