stream/mts: renamed Format function for metadata to Encode

stream/mts/meta.go

@@ -84,7 +84,7 @@ func (m *Meta) Delete(key string) error {
 	return errors.New("Trying to delete map entry that doesn't exist")
 }
 
-func (m *Meta) Format() []byte {
+func (m *Meta) Encode() []byte {
 	// TODO: complete this
 	return []byte("someData")
 }