half way through issue #1

- changed `iii_v.ternary` methods to `classinstancemethod`s
- started turning `iii_v.zinc_blende_.ternary.Ternary` instances into
subclasses of Ternary
- need to finish turning `iii_v.zinc_blende_.ternary.Ternary` instances
into subclasses of Ternary