Add Replies feature (#5)

* add replies payload and method

* clean comment

* improve TextWithReplies and  spelling correction

* fix last typo

receiving.go

@@ -55,6 +55,16 @@ type Attachment struct {
 	Payload Payload `json:"payload"`
 }
 
+// QuickReply is a file which used in a message.
+type QuickReply struct {
+	// ContentType is the type of reply
+	ContentType string `json:"content_type"`
+	// Title is the reply title
+	Title string `json:"title"`
+	// Payload is the  reply information
+	Payload string `json:"payload"`
+}
+
 // Payload is the information on where an attachment is.
 type Payload struct {
 	// URL is where the attachment resides on the internet.

response.go

@@ -24,10 +24,16 @@ type Response struct {
 
 // Text sends a textual message.
 func (r *Response) Text(message string) error {
+	return r.TextWithReplies(message, nil)
+}
+
+// TextWithReplies sends a textual message with some replies
+func (r *Response) TextWithReplies(message string, replies []QuickReply) error {
 	m := SendMessage{
 		Recipient: r.to,
 		Message: MessageData{
-			Text: message,
+			Text:         message,
+			QuickReplies: replies,
 		},
 	}
 
@@ -178,9 +184,10 @@ type SendMessage struct {
 	Message   MessageData `json:"message"`
 }
 
-// MessageData is a text message to be sent.
+// MessageData is a text message with optional replies to be sent.
 type MessageData struct {
-	Text string `json:"text,omitempty"`
+	Text         string       `json:"text,omitempty"`
+	QuickReplies []QuickReply `json:"quick_replies,omitempty"`
 }
 
 // SendStructuredMessage is a structured message template.