Update to use go modules (#671)

This includes updates to CI config, vendor files, etc.
I've hard-coded the k8s depedency at 1.13.4 to keep it inline with what
we currently have and to make sure a another run of `go mod tidy`
doesn't accidentally update it to an unexpected version.

Thanks to hectorj2f for carrying this along.

vendor/github.com/docker/spdystream/CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing to SpdyStream
+
+Want to hack on spdystream? Awesome! Here are instructions to get you
+started.
+
+SpdyStream is a part of the [Docker](https://docker.io) project, and follows
+the same rules and principles. If you're already familiar with the way
+Docker does things, you'll feel right at home.
+
+Otherwise, go read
+[Docker's contributions guidelines](https://github.com/dotcloud/docker/blob/master/CONTRIBUTING.md).
+
+Happy hacking!

vendor/github.com/docker/spdystream/MAINTAINERS

@@ -0,0 +1,28 @@
+# Spdystream maintainers file
+#
+# This file describes who runs the docker/spdystream project and how.
+# This is a living document - if you see something out of date or missing, speak up!
+#
+# It is structured to be consumable by both humans and programs.
+# To extract its contents programmatically, use any TOML-compliant parser.
+#
+# This file is compiled into the MAINTAINERS file in docker/opensource.
+#
+[Org]
+	[Org."Core maintainers"]
+		people = [
+			"dmcgowan",
+		]
+
+[people]
+
+# A reference list of all people associated with the project.
+# All other sections should refer to people by their canonical key
+# in the people section.
+
+	# ADD YOURSELF HERE IN ALPHABETICAL ORDER
+
+	[people.dmcgowan]
+	Name = "Derek McGowan"
+	Email = "derek@docker.com"
+	GitHub = "dmcgowan"

vendor/github.com/docker/spdystream/README.md

@@ -0,0 +1,77 @@
+# SpdyStream
+
+A multiplexed stream library using spdy
+
+## Usage
+
+Client example (connecting to mirroring server without auth)
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/docker/spdystream"
+	"net"
+	"net/http"
+)
+
+func main() {
+	conn, err := net.Dial("tcp", "localhost:8080")
+	if err != nil {
+		panic(err)
+	}
+	spdyConn, err := spdystream.NewConnection(conn, false)
+	if err != nil {
+		panic(err)
+	}
+	go spdyConn.Serve(spdystream.NoOpStreamHandler)
+	stream, err := spdyConn.CreateStream(http.Header{}, nil, false)
+	if err != nil {
+		panic(err)
+	}
+
+	stream.Wait()
+
+	fmt.Fprint(stream, "Writing to stream")
+
+	buf := make([]byte, 25)
+	stream.Read(buf)
+	fmt.Println(string(buf))
+
+	stream.Close()
+}
+```
+
+Server example (mirroring server without auth)
+
+```go
+package main
+
+import (
+	"github.com/docker/spdystream"
+	"net"
+)
+
+func main() {
+	listener, err := net.Listen("tcp", "localhost:8080")
+	if err != nil {
+		panic(err)
+	}
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			panic(err)
+		}
+		spdyConn, err := spdystream.NewConnection(conn, true)
+		if err != nil {
+			panic(err)
+		}
+		go spdyConn.Serve(spdystream.MirrorStreamHandler)
+	}
+}
+```
+
+## Copyright and license
+
+Copyright © 2014-2015 Docker, Inc. All rights reserved, except as follows. Code is released under the Apache 2.0 license. The README.md file, and files in the "docs" folder are licensed under the Creative Commons Attribution 4.0 International License under the terms and conditions set forth in the file "LICENSE.docs". You may obtain a duplicate copy of the same license, titled CC-BY-SA-4.0, at http://creativecommons.org/licenses/by/4.0/.