Update vendor (slack)

vendor/github.com/nlopes/slack/examples/ims/ims.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/nlopes/slack"
+)
+
+func main() {
+	api := slack.New("YOUR_TOKEN_HERE")
+
+	userID := "USER_ID"
+
+	_, _, channelID, err := api.OpenIMChannel(userID)
+
+	if err != nil {
+		fmt.Printf("%s\n", err)
+	}
+
+	api.PostMessage(channelID, "Hello World!", slack.PostMessageParameters{})
+}