Add Slack support

vendor/github.com/nlopes/slack/websocket_stars.go

@@ -0,0 +1,14 @@
+package slack
+
+type starEvent struct {
+	Type           string      `json:"type"`
+	User           string      `json:"user"`
+	Item           StarredItem `json:"item"`
+	EventTimestamp string      `json:"event_ts"`
+}
+
+// StarAddedEvent represents the Star added event
+type StarAddedEvent starEvent
+
+// StarRemovedEvent represents the Star removed event
+type StarRemovedEvent starEvent