title: Customize argparse help message
body: <p>I have written the following sample code to demonstrate my issue.</p>
  
  <pre><code>import argparse
  
  parser = argparse.ArgumentParser()
  parser.add_argument('-v', '--version', action='version',
                      version='%(prog)s 1.0')
  parser.parse_args()
  </code></pre>
  
  <p>This produces the following help message.</p>
  
  <pre><code>$ python foo.py --help
  usage: foo.py [-h] [-v]
  
  optional arguments:
    -h, --help     show this help message and exit
    -v, --version  show program's version number and exit
  </code></pre>
  
  <p>I want to customize this help output such that it capitalizes all phrases and sentences, and puts period after sentences. In other words, I want the help message to be generated like this.</p>
  
  <pre><code>$ python foo.py --help
  Usage: foo.py [-h] [-v]
  
  Optional arguments:
    -h, --help     Show this help message and exit.
    -v, --version  Show program's version number and exit.
  </code></pre>
  
  <p>Is this something that I can control using the argparse API. If so, how? Could you please provide a small example that shows how this can be done?</p>