Add Pareto Frontier Plot Functionality

[mnagired]

Create class / function which takes in a two lists of values for separate metrics (e.g. accuracy and disparate impact ratio) and generate + display the Pareto frontier.

Guidance on how to get the Pareto frontier can be found here.

[hoffmansc]

See also: demo_reject_option_classification.ipynb

I'm thinking it should look vaguely like DecisionBoundaryDisplay where there is a from_estimator classmethod which takes a GridSearchCV class with 2 scorers and looks at the cv_results_

[MiKueen]

Hi @hoffmansc @mnagired, I would like to work on this issue.