Allow input of pathlib2 paths instead of file names
Created originally on Bitbucket by gappleto97
pathlib2 is a backported version of pathlib, so that people can use the latest version instead of the one that comes with Python (if it comes with it at all).
At the moment, when you feed it a path from pathlib, both load_workbook and workbook.save throw errors.
For load_workbook, it is because it calls os.stat, and for workbook.save, it is because it tries to call the tell() method of the path, which does not exist.