0.23.0

• [Breaking change] encode/1 returns a tuple, use encode!/1 to get the old behaviour of encode/1
• Raise RequiredFieldsError when encoding or decoding a Protobuf 2 message with unset required fields (that is, that have the value nil)
• Raise IllegalTagError when decoding a message with a tag set to 0
• ~+40% speedup & ~-30% memory consumption when decoding thanks to macro
• Fix missing encoding of unknown fields when a message hadn't any field