Extended RunDoctestsScript.

You may now instantiate a RunDoctestsScript instance and then pass an explicit
list of paths-to-be-test using the new file_paths=None keyword implemented on
RunDoctestsScript.process_args().

Example:

    file_paths = file_path_getting_method()
    script = developerscripttools.RunDoctestsScript()
    script.process_args(file_paths=file_paths)