Instanciate common attributes everywhere so one can simply use the extend method

feed.go

@@ -28,9 +28,10 @@ type Feed struct {
 // NewFeed creates a new Feed. It returns a *Feed.
 func NewFeed(title string) *Feed {
 	return &Feed{
-		ID:      NewID(NewURN()),
-		Title:   NewText("text", title),
-		Updated: NewDate(time.Now()),
+		CommonAttributes: newCommonAttributes(),
+		ID:               NewID(NewURN()),
+		Title:            NewText("text", title),
+		Updated:          NewDate(time.Now()),
 	}
 }