Adds Stateful Set Basics as a tutorial

The content is in
docs/tutorials/stateful-applications/basic-stateful-set.md
The example application, named web, is in
docs/tutorials/stateful-applications/web.yaml
The tutorials TOC and index have been udpated to include a Stateful
Applications section of which this example is a subsection

docs/tutorials/stateful-application/web.yaml

@@ -0,0 +1,47 @@
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx
+  labels:
+    app: nginx
+spec:
+  ports:
+  - port: 80
+    name: web
+  clusterIP: None
+  selector:
+    app: nginx
+---
+apiVersion: apps/v1beta1
+kind: StatefulSet
+metadata:
+  name: web
+spec:
+  serviceName: "nginx"
+  replicas: 2
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+      - name: nginx
+        image: gcr.io/google_containers/nginx-slim:0.8
+        ports:
+        - containerPort: 80
+          name: web
+        volumeMounts:
+        - name: www
+          mountPath: /usr/share/nginx/html
+  volumeClaimTemplates:
+  - metadata:
+      name: www
+      annotations:
+        volume.alpha.kubernetes.io/storage-class: anything
+    spec:
+      accessModes: [ "ReadWriteOnce" ]
+      resources:
+        requests:
+          storage: 1Gi
+