pathToArray changing drive letter case for Windows

[marknadig]

pathToArray() unnecessarily changes the drive letter case when not *nix path[0] = path[0].toUpperCase();.

This mutation causes a problem in tasks run from c:. For example, memory-fs-stream _read() will fail because root was "c:..." but they keys on this.fs.data had been changed by pathToArray to "C:"

I don't see a test asserting this behavior. I'm happy to submit a PR, but wanted to verify this behavior wasn't intentional/required.