`Postprocess` uses an outdated trade history format – migrated to `sqlite` instead of `csv`

[gordonkoehn]

The current version of hummingbot seem to use sqlite instead of csv for storing the trade history.

Thus this script in humminbot_postprocess.py does not work on today's hummingbot output in data/.

This script could probably quite easily be modified to work again.

[gordonkoehn]

@fengtality You reference this script in the botcamp course Market Making Strategies/Running the Pure Market Making Script.

Learning where to gather the data for this kind of analysis is excellent. However, a note that this script is outdated would be helpful for the future students: