chore(http): remove unused properties from Request

This removes properties mentioned in #3339

Closes #3339
Closes #3823

modules/angular2/http.ts

@@ -34,14 +34,7 @@ export {Http, Jsonp} from './src/http/http';
 
 export {Headers} from './src/http/headers';
 
-export {
-  ResponseTypes,
-  ReadyStates,
-  RequestMethods,
-  RequestCredentialsOpts,
-  RequestCacheOpts,
-  RequestModesOpts
-} from './src/http/enums';
+export {ResponseTypes, ReadyStates, RequestMethods} from './src/http/enums';
 export {URLSearchParams} from './src/http/url_search_params';
 
 /**