Make conversations type-safe (last big reorg) (REAL) (NOT CLICKBAIT) In previous versions of Conversation, you could send messages and then return messages of the wrong type or in the wrong order or whatever. The receiver would then have to make sure that there were the right number of messages and that each message was the right type. That's annoying. This change makes the `Message` enum a two-way channel, where the asker puts their question into it, and then the answerer (the conversation) puts the answer in and returns control to the asker. The asker then only has to pull the Answer of the type they wanted out of the message.

350579171e1ff1cef0f1ec1d649cb6df29218952 v0.0.1
bc5e18fa9c7a661b70bc73bdca3520a16cb2ebbc v0.0.2
52f1102e0715e92afeda3c3d859c1cb94a23c4d5 v0.0.3
2a5c83d04b93ef27b1c59d52a0aff46febd920ab v0.0.4
bbe84835d6db43d15b831fbec1c914139c3d8eaf v0.0.5
71e432a213ee099a94655464845c10cdc2e84034 v0.0.6