Add the start of a (video-recorded) HTTP/2 Client implementation.

adg and I recorded ourselves writing this: https://golang.org/s/http2clientvideo
diff --git a/transport_test.go b/transport_test.go
new file mode 100644
index 0000000..dd98816
--- /dev/null
+++ b/transport_test.go
@@ -0,0 +1,29 @@
+// Copyright 2015 The Go Authors.
+// See https://go.googlesource.com/go/+/master/CONTRIBUTORS
+// Licensed under the same terms as Go itself:
+// https://go.googlesource.com/go/+/master/LICENSE
+
+package http2
+
+import (
+	"flag"
+	"net/http"
+	"os"
+	"testing"
+)
+
+var extNet = flag.Bool("extnet", false, "do external network tests")
+
+func TestTransport(t *testing.T) {
+	if !*extNet {
+		t.Skip("skipping external network test")
+	}
+	req, _ := http.NewRequest("GET", "https://http2.golang.org/", nil)
+	var rt http.RoundTripper = &Transport{}
+	//rt = http.DefaultTransport
+	res, err := rt.RoundTrip(req)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	res.Write(os.Stdout)
+}