outyet: update example, make a separate module

We want to revive golang.org/x/example as a test case for
an experiment with a 'gonew' command.

This CL updates outyet to be a gonew-able sample server,
by making it its own module. The CL also removes
Dockerfile and containers.yaml because I think the
best practices around those files have evolved too much
since 2015 when they were written.

Change-Id: I53faf4b30de9e4ef3bfe35a781732daa140a9877
Reviewed-on: https://go-review.googlesource.com/c/example/+/513998
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Cameron Balahan <cbalahan@google.com>

Author: rsc

README.md

@@ -37,6 +37,21 @@ The [reverse](hello/reverse/) reverse covers:
 * Conversion between string and []rune
 * Table-driven unit tests ([testing](//golang.org/pkg/testing/))
 
+## [helloserver](helloserver/)
+
+```
+$ cd helloserver
+$ go run .
+```
+
+A trivial "Hello, world" web server.
+
+Topics covered:
+
+* Command-line flags ([flag](//golang.org/pkg/flag/))
+* Logging ([log](//golang.org/pkg/log/))
+* Web servers ([net/http](//golang.org/pkg/net/http/))
+
 ## [outyet](outyet/)
 
 ```

outyet/Dockerfile

@@ -0,0 +1,4 @@
+module golang.org/x/example/outyet
+
+go 1.19
+

outyet/containers.yaml

@@ -19,7 +19,7 @@ import (
 
 // Command-line flags.
 var (
-	httpAddr   = flag.String("http", ":8080", "Listen address")
+	httpAddr   = flag.String("http", "localhost:8080", "Listen address")
 	pollPeriod = flag.Duration("poll", 5*time.Second, "Poll period")
 	version    = flag.String("version", "1.4", "Go version")
 )
@@ -30,6 +30,7 @@ func main() {
 	flag.Parse()
 	changeURL := fmt.Sprintf("%sgo%s", baseChangeURL, *version)
 	http.Handle("/", NewServer(*version, changeURL, *pollPeriod))
+	log.Printf("serving http://%s", *httpAddr)
 	log.Fatal(http.ListenAndServe(*httpAddr, nil))
 }