Ensure path is a string so normalize can function properly

On my desktop (ArchLinux), I get a `TypeError: Object /path/to/file has no method 'charAt'`. For some reason, `path` is being passed in as an `Object` in this case. This change simply ensures a string is used by calling `toString()` so normalize wont freak out.

Interestingly, my Macbook Pro has no issues.