ExploreCohortEvaluation plots shrink as legend grows

[rgleaton]

Problem Summary

The plots generated by seismometer._api.ExploreCohortEvaluation shrink as the legend grows longer.

Impact

As subgroup names get longer, the plots become more difficult to use. In the case of very long subgroup names the plots are nearly unusable.

Possible Solution

Give the legend a maximum size and truncate, wrap, or scale long subgroup names to fit within.

Steps to Reproduce

1. Run sm.ExploreCohortEvaluation()
2. Select a Cohort filter with a subgroup that has a long name
3. Make sure that subgroup is selected
4. Watch the plots shrink