Ordered vs. Unordered Categoricals
I was looking at supporting Categorical objects in statsmodels [1] recently and again now in seaborn [2]. I think it would be great to support both ordered and unordered Categorical variables (via a flag or something). IIRC, there was some discussion about this. Is it possible? From what I could tell all Categorical types are assumed to have some order.

[1] https://github.com/statsmodels/statsmodels/issues/2133
[2] https://github.com/mwaskom/seaborn/issues/361
