slack: new package with Slack's endpoints

Change-Id: Ie461323194d73cdb9600e03abb96356637afc15d
Reviewed-on: https://go-review.googlesource.com/19525
Reviewed-by: Burcu Dogan <jbd@google.com>
diff --git a/slack/slack.go b/slack/slack.go
new file mode 100644
index 0000000..593d2f6
--- /dev/null
+++ b/slack/slack.go
@@ -0,0 +1,16 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package slack provides constants for using OAuth2 to access Slack.
+package slack // import "golang.org/x/oauth2/slack"
+
+import (
+	"golang.org/x/oauth2"
+)
+
+// Endpoint is Slack's OAuth 2.0 endpoint.
+var Endpoint = oauth2.Endpoint{
+	AuthURL:  "https://slack.com/oauth/authorize",
+	TokenURL: "https://slack.com/api/oauth.access",
+}