in quickstart, add -hostname flag and check public ips with 2 dnsbl's

- if the guessed hostname is not correct, you can specify one yourself. useful
  if you generate a config locally and deploy to a different machine.
- if explicit public ips are found, check them with spamhaus and spamcop DNSBLs
  and warn if they are listed, with links to check more DNSBLs. should prevent
  disappointment later on.

docker-compose.yml

@@ -4,6 +4,9 @@
 #	mkdir config data web
 # 	docker-compose run mox mox quickstart you@yourdomain.example $(id -u mox)
 #
+# note: if you are running quickstart on a different machine than you will deploy
+# mox to, use the "quickstart -hostname ..." flag.
+#
 # After following the quickstart instructions you can start mox:
 #
 # 	docker-compose up