Option to prefix help with text

Hi,

I would like an option to prefix the --help output with my program's banner along the top, eg.

```
=====
MyProgram version 1.2.3
=====

  Usage: myprogram [options]
  ... etc...
```

There doesn't seem to be a way to do this right now (at least not just for when the help text gets displayed) - could it be added?
