Comparison of file paths shouldn't use raw strings

[harrysarson]

The path modules normalises strings to the operating system (e.g. / is replaced by \\ on windows).

Therefore comparing paths by using string comparison is dangerous, I think this may be the cause of issue #17.

Possibly using https://nodejs.org/api/path.html#path_path_relative_from_to may be a more robust to compare file paths.