Refactor for demonstration

[janbridley]

I am cleaning up some outstanding issues with this package to make it ready for integration with glotzerlab/coxeter.

TODOs:

• Standardize view distance in preset views.
• Add tests
• Add in some extras
• Remove dependency on coxeter - this should be a convenience, not a requirement
• Rerender example images
• Distribute to separate files
• Add basic CI
• Add example images (similar to original, but choose examples)
• Update readme example 2 to use real mesh
• requirements.txt