Fix split in expandPath

[sake92]

The toURI().relativize returns path with slashes /.
But in the expandPath it splits by File.separator (\ on windows).
That doesn't work on windows, obviously, different characters.

If we use Files.relativize instead of URL we get '\', but then we get these errors:
Check that all literal '$' are properly escaped with '\$'

So the solution is just to split by /.

Fixes #465

[eed3si9n]

Thank you @sake92!
LGTM