New vignette for visualizing performance and feature importance

[kelly-sovacool]

Currently, a lot of plots are buried in the parallel vignette. We should break them out into a separate vignette.

• plots for a single model
  • ROC and PRC
  • Feature importance with 95% CI
• plots for multiple models on same dataset
  • Mean ROC and PRC
  • Performance boxplots with AUROC and AUPRC
  • Feature importance with 95% CI
• plots for model(s) on different datasets with class imbalances
  • Mean balanced PRC
  • Boxplot with AUBPRC