use correct code snippet for Put with complete key

Change-Id: I779d18e1f0fd19c7c5237b20f2be7b2c467b2206

Author: Francesc Campoy

section07/README.md

@@ -72,16 +72,16 @@ non nil if some error occurs while storing the data.
 Let's see an example of how to use the `datastore.Put` function:
 
 
-[embedmd]:# (examples/app.go /func incomplete/ /^}/)
+[embedmd]:# (examples/app.go /func complete/ /^}/)
 ```go
-func incompleteHandler(w http.ResponseWriter, r *http.Request) {
+func completeHandler(w http.ResponseWriter, r *http.Request) {
 	// create a new App Engine context from the HTTP request.
 	ctx := appengine.NewContext(r)
 
 	p := &Person{Name: "gopher", AgeYears: 5}
 
-	// create a new complete key of kind Person.
-	key := datastore.NewIncompleteKey(ctx, "Person", nil)
+	// create a new complete key of kind Person and value gopher.
+	key := datastore.NewKey(ctx, "Person", "gopher", 0, nil)
 	// put p in the datastore.
 	key, err := datastore.Put(ctx, key, p)
 	if err != nil {