Example notebook that installs from PyPI

[rolyp]

Simple test case (possibly an example notebook, but not necessarily) that installs backfillz-py from PyPI into a fresh Python environment, and creates some a few visualisations.

• plots squished in notebook -- Adjust font size/margins in notebook environment #43
• example of plot_trace_dial and plot_slice_histogram
• add nbtest step into test scripts -- Run example notebooks with nbval #42
• verify in Firefox, Safari and Chrome

Done/dropped:

• upload new interim release (0.0.4) to PyPI
• install Miniconda, JupyterLab
• test Jupyter notebook that installs from PyPI
• move Stan class to backfillz.stan
• move Eight Schools example to examples
• pip install backfillz==0.0.5 into JupyterLab environment.
  • change Python version dependency to ^3.9.0 (to allow installation) but < 3.10 (for scipy)
• use nest_asyncio so PyStan will run in JupyterLab
• !jupyter labextension install jupyterlab-plotly otherwise plots don’t render
• RootPlot.render should return go.Figure; plots -> figs (returns all figs);
• Plot.show to run Figure.show with preferred arguments
• API to plot figure per parameter
• root package to export main definitions from subpackages
• extract fig method that returns the go.Figure, so this is transparent to the end user
• hide subplot layout unless verbose explicitly specified
• move plot_xxx methods to Backfillz class?