a first attempt at a more generalized report command that can handle one or two file paths and will search directories and generate multiple reports if needed

I believe this will fix MacOSX not displaying the icon. #30

The move from optparse to argparse caused a regression: positional
arguments could no longer intermix with optional arguments.  This fixes
that. (As of Python 3.7, parse_intermixed_args solves the problem,
but we want to support 2.6, maybe 2.5.)