Clean the path the same way on all platforms

[triple-j]

I was testing --human-folders on Linux and ran into an issue where game names that contain a forward slash (/) would be broken up into multiple folders. So I removed the platform check in clean_path().

This is also better for compatibility. It's rare, but this allows someone to move their folders to different platforms. Since the files/folders are now created the same on all platform, the user won't accidentally re-download files if they run this project on multiple platforms.

[Emersont1]

This is something I'm not sure about. The path cleanup is overzealous for linux and I (personally) am not a fan of the human readable names - I think escaping a / to a - is probably a better change

[triple-j]

I think compatibility across platforms is more important than to allow a few extra characters in Linux filenames.

As I mentioned before, those extra characters can cause problems when dealing with multiple platforms.

Here are some use cases that would be problematic if those extra characters aren't replaced:

• Running itch-download on a Linux NAS and sharing the download folder over Samba (Windows network sharing) to Windows computers.
• Having a Linux/Windows dual boot system. Running itch-download on the Linux partition with the download folder being accessible by Windows.
• Running itch-download on the Linux. Copying the download folder to a USB drive and trying to read that on a Windows system.

Those are issue I've dealt with in the past and is why I always strip out characters that would be problematic for Windows, even if I mainly use Linux.