• Add Encoder.encode_into api, for encoding into an existing buffer without copying
• Add support for encoding/decoding MessagePack extensions
• Add support for encoding/decoding datetime objects
• Add support for encoding/decoding custom objects without relying on MessagePack extensions
• Add support for marking Struct types as hashable
• Add support for serializing Struct types as MessagePack array objects rather than map objects.
• Several performance improvements. On average 50% faster encoding and 30% faster decoding.