Don't use IFrames in notebooks under vscode, add support for altair plot in vscode

[gbowlin]

Overview

Closes #53

Description of changes

Adds the ability to detect the notebook host, so that we can change display behavior based on which host we are in. This is useful when dealing with IFrames in particular, because vscode does not allow them to render local content.

Since the Altair plot for Aequitas doesn't load well as HTML, we have used the host detection ability to choose whether or not we want to save the plot to HTML/IFrame or just display the plot as is.

Testing Instructions

• make sure you can run the default notebook in vscode and see the fairness control and outcomes
• make sure you can run the default notebook via jupyter lab and see the fairness control and outcomes

Author Checklist

• Linting passes; run early with pre-commit hook.
• Tests added for new code and issue being fixed.
• Added type annotations and full numpy-style docstrings for new methods.
• Draft your news fragment in new changelog/ISSUE.TYPE.rst files; see changelog/README.md.