API extensions and fixes for the p5 backend

Last year, as a project under the Google Summer of Code, I created p5 --- a native Python implementation of the Processing API. The goal then was to combine Python's minimal syntax and pedagogical roots with Processing's high-level graphics API. While the project was successful and we released the first alpha as a Python package, p5 is still missing some core parts of the processing API and needs better cross-platform support.

The goal of this project is to fix existing cross-platform issues by changing the internal rendering engine to VisPy; fixing existing open issues; and extending the API by adding image support, improvements to the Shape() class, and minor utility methods.