Clean up remove caddy refs (#139)

* Changed reference to Caddy over to CoreDNS

* Removing references to caddy

* Fixed misleading error message to reference coredns

* Cleaning up references to caddy

* Adding clean and deps targets

Muscle memory is resulting in "make clean" commands.

* Adding test target to makefile

* More "Caddy" cleanup

core/https/user.go

@@ -121,14 +121,14 @@ func newUser(email string) (User, error) {
 // input. If userPresent is false, the operator will
 // NOT be prompted and an empty email may be returned.
 func getEmail(cfg server.Config, userPresent bool) string {
-	// First try the tls directive from the Caddyfile
+	// First try the tls directive from the Corefile
 	leEmail := cfg.TLS.LetsEncryptEmail
 	if leEmail == "" {
 		// Then try memory (command line flag or typed by user previously)
 		leEmail = DefaultEmail
 	}
 	if leEmail == "" {
-		// Then try to get most recent user email ~/.caddy/users file
+		// Then try to get most recent user email ~/.coredns/users file
 		userDirs, err := ioutil.ReadDir(storage.Users())
 		if err == nil {
 			var mostRecent os.FileInfo