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/caddy_test.go

@@ -2,10 +2,10 @@ package core
 
 /*
 func TestCaddyStartStop(t *testing.T) {
-	caddyfile := "localhost:1984"
+	corefile := "localhost:1984"
 
 	for i := 0; i < 2; i++ {
-		err := Start(CaddyfileInput{Contents: []byte(caddyfile)})
+		err := Start(CorefileInput{Contents: []byte(corefile)})
 		if err != nil {
 			t.Fatalf("Error starting, iteration %d: %v", i, err)
 		}