Potential command injection vulnerability in system-ping

Hi,

 We would like to report a potential security vulnerability.
The bug is introduced because the package-exported method `ping` fails to sanitize the parameter and let it flow into a sensitive command execution API.

Here is the proof of concept.
```
const ping = require( 'system-ping' );
ping( '|| touch cmd' )// a file named cmd will be created
```
Please consider fix it. thanks!
