Creating this parent issue to track API improvements / upgrades

1. Support forward references (which will enable recursive dataclasses): Hacky workaround for forward references #5
2. Full typing support: "Type[xxx]" has no attribute "from_json" #23
3. coerce_keys kwarg for encoding: coerce_keys option #29
4. user-supplied overrides user-supplied overrides #42
5. Sharing encoder / decoder in wider scopes (currently must be per-field. type, class, global are all potential scopes) wider config scopes #139