Flag -delegates for delegated domains

Meant for obtaining wildcard certs from Let's Encrypt using the DNS-01
challenge.

- introduce a variant of `blocklist.txt` to be used for testing
  (`blocklist-test.txt`) because the blocklist has grown so large it
  clutters the test output
- more rigorous about lowercasing hostnames when matching against
  customized records. This needs to be extendend when we parse _any_
  arguments

TODOs:

- remove the wildcard DNS servers
- update instructions

integration_speed_test.go

@@ -20,7 +20,7 @@ var _ = Describe("speed", func() {
 	var flags []string
 
 	JustBeforeEach(func() {
-		flags = append(flags, "-port", strconv.Itoa(port), "-blocklistURL", "file://etc/blocklist.txt")
+		flags = append(flags, "-port", strconv.Itoa(port), "-blocklistURL", "file://etc/blocklist-test.txt")
 		serverCmd = exec.Command(serverPath, flags...)
 		serverSession, err = Start(serverCmd, GinkgoWriter, GinkgoWriter)
 		Expect(err).ToNot(HaveOccurred())