Release v2.4.0
What's new:
- Add an ability to use another JSON unmarshaller implementation (#45 by @dreamscached) — 9c0e7de
- Add an ability to use another PNG/Base64 decoders (#47 by @dreamscached) — 30b7b4c
- Implement Stringer interface for user-friendly stringifications (#48 by @dreamscached) — 09cff17