EncodeJSONResponse does not account for http.StatusNoContent

[groob]

The current implementation of EncodeJSONResponse always writes an HTTP response body.
When the status should be http.StatusNoContent, there shouldn't be any response body.

In my own code I've done a check like this:

    if e, ok := response.(statusCoder); ok {
        w.WriteHeader(e.status())
        if e.status() == http.StatusNoContent {
            return nil
        }
    }

Should the EncodeJSONResponse have a check for 204 responses? I can send a PR but wanted to make sure it's wanted first.

[basvanbeek]

I personally would expect it to play nice with expectations so +1 from me

[peterbourgon]

SGTM!