Make sure to test on Windows locally

[Vindaar]

We're currently (#15) disabling every command that actually runs stuff in a terminal on Windows CI, since the commands error. Most likely because random unix commands simply don't exist.

But need to make sure that there isn't another bug somewhere that makes the whole library not work on Windows. If so replace tests by things that work on Windows too?

[Vindaar]

This was at least partially for two different reasons:

1. windows raises OSError if a command is not found (in startProcess)
2. we have to supply poUsePath manually, because it's normally used by default on windows iiuc.

Still should be tested manually before this is closed.

Also:
one and pipe on windows are broken!