0.3.0

Unit enum variants are now serialized as strings instead of maps (#16)

Consider the following enum:

enum E { V, W }

A map containing keys "v" and "w" and values E::V and E::W used to be serialized as:

v:
  V: []
w:
  W: []

Now it will be serialized as:

v: V
w: W

Deserialization supports both the old and the new format.

This aligns with the corresponding change in serde_json 0.8.0.