docs(http): update http docs to mention .map operator

Closes #5947

modules/@angular/http/src/http.ts

@@ -43,6 +43,7 @@ function mergeOptions(defaultOpts: BaseRequestOptions, providedOpts: RequestOpti
  *
  * ```typescript
  * import {Http, HTTP_PROVIDERS} from '@angular/http';
+ * import 'rxjs/add/operator/map'
  * @Component({
  *   selector: 'http-app',
  *   viewProviders: [HTTP_PROVIDERS],
@@ -64,7 +65,7 @@ function mergeOptions(defaultOpts: BaseRequestOptions, providedOpts: RequestOpti
  * ### Example
  *
  * ```
- * http.get('people.json').observer({next: (value) => this.people = value});
+ * http.get('people.json').subscribe((res:Response) => this.people = res.json());
  * ```
  *
  * The default construct used to perform requests, `XMLHttpRequest`, is abstracted as a "Backend" (