Add basic interactive overwrite strategy

Available options:

- Do not copy
- Overwrite dest
- Copy source as dest.dist

cmd/scaffold/main.go

@@ -16,7 +16,7 @@ func main() {
 	}
 
 	if err := app.Run(os.Args); err != nil {
-		fmt.Printf("%+v", err)
+		fmt.Printf("%+v\n", err)
 		os.Exit(1)
 	}
 }