no-overwrite option

Is it possible that you have a "non-overwrite" option? (noclobber)...

for example, if we downloaded a video some 2 months ago and forgot and we download it again, it may download all over again.

1. If that file was perfectly ok, now we just erase it and start all over, so there is some risk if it doesn't succeed this time. Why erase a perfectly good file just to download it again?
2. If it took 45 minutes to download last time, why spend again 45 minutes to download? If we Ctrl-C after two minutes, then viola, that file was gone and now it is ruined by having a fraction of the file. We need to go through 45 minute pain to wait for the download again.

P.S. Ok, I guess we can check it ourselves... before doing the `ytdl()...` and `.pipe(fs.createWriteStream(filenameToUse));` we can use

```js
if (fs.existsSync(filenameToUse)) {
throw new Error("File already exists!!!");
}
```