update readme example of config.py

[nsandler1]

closes #86

[tybug]

I don't think we should be concerned about keeping this strictly up to date (that's why I wrote "something like this" instead of "exactly like this", for future proofing), but sure. We'll also probably want to reword things at some point to not include the full file, otherwise half the readme will be the full text of the config file.