Change PosixPath to Path for Windows Users

[ghost]

Issue: Running Bayesmark on Windows using Cygwin throws an exception in cmd_parse.py. This is because PosixPath does not work in Windows.

Resolution: Instead of using PosixPath, use Path instead. Instantiating Path creates either a PosixPath or a WindowsPath depending on the OS. See here: https://docs.python.org/3/library/pathlib.html#pathlib.Path