Add a Data Formats Guide

[jnothman]

Transforming your input data can be challenging. We should help with a guide in the documentation.

I think the guide should present the following cases:

• Representing counts only
• Representing data elements and their associated sets
• Representing additional attributes for each data element

and do so for various ways of data representation

[jnothman]

Should also consider supporting the delimited-string representation of multiple categories that is provided by pandas.Series.str.get_dummies(sep='|')

[SichongP]

Hi, I ran into this repo yesterday and have been very happy about its existence. I'd like to help work on the documentation as I spent quite a while figuring out data format myself yesterday...

If you can point me to the right file/directory I can try to start working on some documentation.

[jnothman]

See under the doc/ directory. You can create a new .rst file there, and once you're on your way to a first draft, feel free to open a pull request. Thanks