title: ArgumentParser epilog and description formatting in conjunction with ArgumentDefaultsHelpFormatter
body: <p>I'm using <a href="http://docs.python.org/dev/library/argparse.html" rel="noreferrer">argparse</a> to take in command line input and also to produce help text. I want to use <code>ArgumentDefaultsHelpFormatter</code> as the <code>formatter_class</code>, however this prevents me from also using  <code>RawDescriptionHelpFormatter</code> which would allow me to add custom formatting to my description or epilog.</p>
  
  <p>Is there a sensible method of achieving this aside from writing code to produce text for default values myself? According to the argparse docs, all internals of <code>ArgumentParser</code> are considered implementation details, not public API, so sub-classing isn't an attractive option.</p>