docs: Add link to code review instance to README

Fixes #318

Change-Id: Ibb89806e0e45d4848e7fce2ae5c72fc72ad2f92c
Reviewed-on: https://code-review.googlesource.com/c/36190
Reviewed-by: Chris Broadfoot <cbro@google.com>
diff --git a/README.md b/README.md
index 530b375..cd938c1 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@
 * For a longer tutorial, see the [Getting Started guide](https://github.com/google/google-api-go-client/blob/master/GettingStarted.md).
 * For examples, see the [examples directory](https://github.com/google/google-api-go-client/tree/master/examples).
 * For support, use the [golang-nuts](https://groups.google.com/group/golang-nuts) mailing list.
+* The code review instance may be found [here](https://code-review.googlesource.com).
 
 ## Status
 [![GoDoc](https://godoc.org/google.golang.org/api?status.svg)](https://godoc.org/google.golang.org/api)