Create unit testing framework

[shankari]

Before we go too deep into building out features, I want to make sure that we have a unit testing framework in place.
Although it has an initial upfront cost, as we add additional complexity to the dashboard, it will save us significant time down the road.

Suggestions for enabling unit testing using dash are at:
https://dash.plotly.com/testing

At a minimum, we should enable the testing of the python-based callbacks, with mocking as needed.
We should to add at least one end-to-end test to sanity test the UI