I put up a PR to address #89, hope that's fine?

I branched it from the 0.2.3 release tag because tests were failing current master.

Hi, possibly a stupid question, but I don't understand how response coercion is supposed to work at all

The spec -response-coercer of the spec Coercion just ends up calling st/conform, which would never call st/encode. So nothing ever calls encoders, only decoders

(which is what you'd want for request, but not for response, I'd have assumed)