add epilog

[aberezin]

This PR adds an epilog to the options (like ARGPARSE_DESCRIPTION is optional)

[nhoffman]

@aberezin - thanks for the contribution! Can you please update your changes to the test code to retain python2 compatibility?

% python2 test.py
  File "test.py", line 12
    def run(script,*args,expect_exit_1=False):
                                     ^
SyntaxError: invalid syntax

also, I try to stick with with PEP8 formatting rules. I'd be happy to merge an updated PR.