chore(http): update http example to include map operator

modules/playground/src/http/http_comp.ts

@@ -1,5 +1,6 @@
 import {Component, View, NgFor} from 'angular2/angular2';
 import {Http, Response} from 'angular2/http';
+import 'rxjs/operators/map';
 
 @Component({selector: 'http-app'})
 @View({
@@ -16,6 +17,8 @@ import {Http, Response} from 'angular2/http';
 export class HttpCmp {
   people: Object[];
   constructor(http: Http) {
-    http.get('./people.json').subscribe(res => { this.people = res.json(); });
+    http.get('./people.json')
+        .map((res: Response) => res.json())
+        .subscribe((people: Array<Object>) => this.people = people);
   }
 }