Ensure paths with escaped characters produce platform-independent script names

[nblumhardt]

Relative script filenames should produce the same persisted script name on all platforms. Currently, path separators are replaced with / uniformly, but e.g. escaped spaces and escaped separators may cause script names to differ depending on the platform from which Piggy is run.

[todthomson]

I'm presuming the fix is to be found here: https://github.com/datalust/piggy/blob/dc81fb3af7a526e28093d137b4316c14edbccf6b/src/Datalust.Piggy/Filesystem/ChangeScriptFileEnumerator.cs#L24