Switched from 'optparse' to 'argparse' (bundled with Python 2.7; install separately on earlier version). Extracted methods.
Use a named tuple (requires Python 2.6 or later).
Use a simple reduce function instead of a heap to select the biggest files.
Use modern string formatting (requires Python 2.6 or later).
Extracted method to generate formatted result lines.
Added docstrings. Renamed function.
Made compatible with Python 3.
Use 'pathlib' (bundled as of Python 3.4; install separately on older versions).