Notebook documentation of Toy Model

[drphilmarshall]

Time to work on our legacy: Future Ale and Future Phil are going to appreciate seeing which experiments have been done, and what results they gave.

• [x] Phil: Start a notebook to document the simplest possible scaling relation inference (Mstar-Mhalo given a sample of galaxies with "observed" Mstar and Mhalo, and check it in. Done.
• [x] Phil: Add a PGM written in daft. Done.
• [x] Ale: Add minimal text describing the experiment and a complete set of equations describing our choices for the PDFs and scaling relation. Done
• [x] Ale: Show corner plot of inferred hyperparameters. Done
• [ ] Ale: Optionally: show plots (animation?) or each individual lens' parameters

The actual analysis for this toy model is issued in epic #8.

[drphilmarshall]

Alright @astrosonnen, PGM is done, see what you think. The notebook is all yours to complete! Have fun :-)