clarify logs and gitignore and skipping vendor from now on

Former-commit-id: c8b61b58379d768f04e1593c2a77cf429407cf62

main.go

@@ -20,7 +20,7 @@ func main() {
 	if err := config.New(); err != nil {
 		panic(err)
 	}
-	log.Println(config.Values())
+	log.Println("[main]", config.Values())
 
 	m, err := monitor.New()
 	if err != nil {
@@ -50,7 +50,7 @@ func main() {
 
 func InterruptAfter(foo func() error, c chan os.Signal) {
 	if err := foo(); err != nil {
-		log.Println(err)
+		log.Println("[InterruptAfter]", err)
 	}
 	c <- syscall.SIGINT
 }