feat(typings): add typing specs

add test in gulpfile which will compile a basic TS file with generated
angular2.d.ts to ensure generated d.ts is valid syntactic TS

Adds support for enums in .d.ts generation pipeline.
Removes renaming reexports in http module.

modules/angular2/http.ts

@@ -16,9 +16,19 @@ export {Request} from 'angular2/src/http/static_request';
 export {Response} from 'angular2/src/http/static_response';
 
 export {Http, XHRBackend, XHRConnection, BaseRequestOptions, RequestOptions, HttpFactory};
-export {IHttp} from 'angular2/src/http/interfaces';
+export {
+  IHttp,
+  IRequestOptions,
+  IRequest,
+  IResponse,
+  Connection,
+  ConnectionBackend
+} from 'angular2/src/http/interfaces';
 export {Headers} from 'angular2/src/http/headers';
 
+export * from 'angular2/src/http/enums';
+export {URLSearchParams} from 'angular2/src/http/url_search_params';
+
 /**
  * Provides a basic set of injectables to use the {@link Http} service in any application.
  *