negotiator.go
func NewContentNegotiator(defaultEncoder Encoder, responseWriter http.ResponseWriter) *ContentNegotiator {
	result := &ContentNegotiator{}
	result.DefaultEncoder = defaultEncoder
	result.ResponseWriter = responseWriter
	return result
}
func NewContentNegotiator(defaultEncoder Encoder, responseWriter http.ResponseWriter) *ContentNegotiator {
	result := &ContentNegotiator{}
	result.DefaultEncoder = defaultEncoder
	result.ResponseWriter = responseWriter
	return result
}
// NewContentNegotiator creates a basic ContentNegotiator with out any attached
// encoders