Support Article objects

Includes a new Name field for them to use.

activitystreams/activity.go

@@ -41,6 +41,7 @@ type Object struct {
 	AttributedTo string            `json:"attributedTo"`
 	To           []string          `json:"to"`
 	CC           []string          `json:"cc,omitempty"`
+	Name         string            `json:"name,omitempty"`
 	Content      string            `json:"content"`
 	ContentMap   map[string]string `json:"contentMap,omitempty"`
 }
@@ -56,3 +57,15 @@ func NewNoteObject() *Object {
 	}
 	return &o
 }
+
+func NewArticleObject() *Object {
+	o := Object{
+		BaseObject: BaseObject{
+			Type: "Article",
+		},
+		To: []string{
+			toPublic,
+		},
+	}
+	return &o
+}