Add a markdown or jupyter notebook outside of tutorial showing schematics

So that people can see and select their model

Probably the way to solve this and #3 is to add a "Brief tour" notebook (in root), that starts at L5, then L4, then L3, then straight to L0. Building up, it provides the parameter values for parameters as they are introduced. Instead of saying which bits are simplified away, it says which new features are added