Use vertex array objects

[rreusser]

They're available. Need to figure out the details. https://github.com/regl-project/regl/blob/master/API.md#vertex-array-objects

[rreusser]

Addressed in 2.2.1. My implementation could use some streamlining, and it seems like regl has a bug with VAO emulation, filed here: regl-project/regl#633