wrong prog name

[sverhoeven]

When I have a parser like

parser = argparse.ArgumentParser(
                    description='What the program does',
                    epilog='Text at the bottom of help')

Then the rendered paged shows Documentation for the mkdocs script..

This package can not know the program name so it uses os.path.basename(sys.argv[0]) to get mkdocs.

It would be nice if an warning was printed when prog argument is not given in ArgumentParser constructor.