fix #2: add --create-config to create a default config file

cmd/root.go

@@ -52,6 +52,16 @@ func Execute(output io.Writer) int {
 		return 0
 	}
 
+	if conf.CreateConfig {
+		msg, err := conf.WriteConfigFile()
+		if err != nil {
+			return Die(err)
+		}
+
+		fmt.Fprintln(output, msg)
+		return 0
+	}
+
 	if conf.StoreProgress {
 		progress, err := GetProgress(conf)
 		if err == nil {