Adds support for Windows filepaths by accepting both 0 and 2 as valid return values from validate_file (a return value of 2 means that the path is a Windows filepath, which is normal and expected on a Windows system).
Abstracts the process of validating files for inclusion to a generic function.
0and2as valid return values fromvalidate_file(a return value of2means that the path is a Windows filepath, which is normal and expected on a Windows system).Fixes #219