docs(http): add language annotations and fix method value to enum

Closes #4348

modules/angular2/src/http/static_request.ts

@@ -24,16 +24,16 @@ import {
  * One such example is when creating services that wrap higher-level services, like {@link Http},
  * where it may be useful to generate a `Request` with arbitrary headers and search params.
  *
- * ```
+ * ```typescript
  * import {Injectable, Injector} from 'angular2/angular2';
- * import {HTTP_BINDINGS, Http, Request} from 'angular2/http';
+ * import {HTTP_BINDINGS, Http, Request, RequestMethods} from 'angular2/http';
  *
  * @Injectable()
  * class AutoAuthenticator {
  *   constructor(public http:Http) {}
  *   request(url:string) {
  *     return this.http.request(new Request({
- *       method: 0, //GET.
+ *       method: RequestMethods.Get,
  *       url: url,
  *       search: 'password=123'
  *     }));