Update vendor with go dep

This fix updates vendor with `go dep`

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

vendor/cloud.google.com/go/cloud.go

@@ -0,0 +1,20 @@
+// Copyright 2014 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package cloud is the root of the packages used to access Google Cloud
+// Services. See https://godoc.org/cloud.google.com/go for a full list
+// of sub-packages.
+//
+// This package documents how to authorize and authenticate the sub packages.
+package cloud // import "cloud.google.com/go"