include colinearity discussion?

[lisa55asil]

should we flag new users about problems with possible colinearity issues if their metadata categories are too similar (e.g. including a continuous value of BMI and a quartile category of BMI)?

[mortonjt]

Not exactly sure how to do that in the context of multinomial regression yet.

Maybe we could just do a tutorial with biplots / summary statistics. There is now a pseudo R2 statistic in the qiime2 commands that allow for those sorts of investigations.