Shades 🕶️

The main branch for this is now for shades v2 which is still a work in progress (finding and fixing bugs).

There's a bunch of bug fixing and optimisation to come, but I've overhauled the API now to:

• use lazy evaluation to allow some efficiencies
• shift a lot of the computation over into numpy for efficiency
• improve the api with some nicer functional patterns around the canvas object