Binder_test_minimal

1. Trying to reset to nothing but the README.md and full environment.yml. SUCCESS!
2. Adding a minimal notebook to top level. chi_squared_tests.ipynb works! SUCCESS!
3. Adding one of the subdirectories. Without figures. Setup with just exercise_Intro* notebooks. Was able to load quickly and run the notebook. SUCCESS!
4. Adding the full Setup directory, including figs/ subdirectory.