README.md: release notes for new version

I will push the v0.13.0 tag immediately after this is submitted.

Change-Id: I15c68dad82d772c878af0ab8de1505ba76f7dd65
Reviewed-on: https://code-review.googlesource.com/16710
Reviewed-by: Ross Light <light@google.com>
diff --git a/README.md b/README.md
index 6908b67..4857b1d 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,29 @@
 
 ## News
 
+_September 8, 2017_
+
+*v0.13.0*
+
+- bigquery: UseLegacySQL options for CreateTable and QueryConfig. Use these
+  options to continue using Legacy SQL after the client switches its default
+  to Standard SQL.
+
+- bigquery: Support for updating dataset labels.
+
+- bigquery: Set DatasetIterator.ProjectID to list datasets in a project other
+  than the client's. DatasetsInProject is no longer needed and is deprecated.
+
+- bigtable: Fail ListInstances when any zones fail.
+
+- spanner: support decoding of slices of basic types (e.g. []string, []int64,
+  etc.)
+
+- logging/logadmin: UpdateSink no longer creates a sink if it is missing
+  (actually a change to the underlying service, not the client)
+
+- profiler: Service and ServiceVersion replace Target in Config.
+
 _August 22, 2017_
 
 *v0.12.0*