Video IDs starting with - may be parsed as an option

When using the global `ytdl` command from a terminal, simply using the raw video ID as an argument may cause the ID to be parsed as an option, rather than the actual video ID. This causes `ytdl` to output an error similar to `error: unknown option '-X1X7HuFHSg'`. While an easy workaround would be to use a prefix such as `http://youtu.be/`, I figured I should still open an issue as this is likely not intended behavior.

## Examples
### What happened
```console
command-demo@somelinuxdistro:~# ytdl -i -X1X7HuFHSg
error: unknown option '-X1X7HuFHSg'
```
### What should happen
```console
command-demo@somelinuxdistro:~# ytdl -i -X1X7HuFHSg
title: The Extreme Diet Coke & Mentos Experiments II - The Domino Effect
author: EepyBird
...
```