Known issues
============

- The stereochemistry of allenes is uncaptured. This kind of stereochemistry
  doesn't fit neatly into either category of stereopermutators, and will need
  special treatment.
- Aromaticity is not captured in bond types, and there is representational
  freedom for conjugated systems. Spatial modeling does not make bond distances
  in aromatic cycles uniform.
- Ranking can be slow in complex cases