RFC on Proposal 98

[Sam Barker]

I'd like to get what should be a small cleanup change into the release this week, clarifying the threading contract of KafkaProxy. 

While KafkaProxy isn't technically a public API I felt like a proposal was the right place to think about the contract and threading rules. So I'm also keen to hear what everyone else thinks, was this a good use of the proposal process or was it overkill?

Sam