container: better naming

pkg/container/packaging.go

@@ -45,7 +45,7 @@ func (h header) encoder(w io.Writer) *payloadWriter {
 	return res
 }
 
-func decodePayload(r io.Reader) (io.Reader, error) {
+func payloadDecoder(r io.Reader) (io.Reader, error) {
 	headerBuf := make([]byte, 1)
 	_, err := r.Read(headerBuf)
 	if err != nil {

pkg/container/reader.go

@@ -35,7 +35,7 @@ func FromString(s string) (Reader, error) {
 
 // FromReader decodes a container from an io.Reader.
 func FromReader(r io.Reader) (Reader, error) {
-	payload, err := decodePayload(r)
+	payload, err := payloadDecoder(r)
 	if err != nil {
 		return nil, err
 	}