Add Environment Guide example.

This example shows a simple two tier setup in Kubernetes, and
simply prints the environment information that each pod sees.
Querying the service multiple times will show services at work
load balancing requests.

examples/environment-guide/containers/backend/backend.go

@@ -0,0 +1,37 @@
+/*
+Copyright 2015 The Kubernetes Authors 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 main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+)
+
+func printInfo(resp http.ResponseWriter, req *http.Request) {
+	name := os.Getenv("POD_NAME")
+	namespace := os.Getenv("POD_NAMESPACE")
+	fmt.Fprintf(resp, "Backend Container\n")
+	fmt.Fprintf(resp, "Backend Pod Name: %v\n", name)
+	fmt.Fprintf(resp, "Backend Namespace: %v\n", namespace)
+}
+
+func main() {
+	http.HandleFunc("/", printInfo)
+	log.Fatal(http.ListenAndServe(":5000", nil))
+}