Better scale
Show two views of sphere
Show a single green tile
Fix rotation, only use slider
Add sparse list class
Use dicts instead of deques
Remove edges
Use ids instead of references
Some notes
Replace tile/corner logic with face/vertex

Each grid has two dictionaries, of foces' center locations to lists of
their vertices' locations, and of vertex locations to sets of their
faces' centers' locations. In all cases values are 3-space vectors.

Vectors are summed "in order" so that floating point errors don't cause
the same values to hash differently.
Remove old subgrid logic
Add subgrid method
Move subtile logic to SubGrid class

A SubGrid is constructed with a reference to its parent Grid; it is
populated by calling the self-mutating populate method with the location
of the parent's face to be subdivided.
Move vector functions outside of Grid class
Show individual layers
Remove tile/corner stuff
Wrap subgrid logic into grid class
Move Grid definition to its own file
Shade faces randomly