title: Angular2 RC5 Default http headers
body: <p>There was possibility to extend Http or BaseRequestOptions in RC4
  and add default headers to all http requests.
  Like here <a href="https://stackoverflow.com/questions/34969292/how-to-set-default-http-header-in-angular2">How to set default HTTP header in Angular2?</a>
  How to do it in RC5 ?</p>
  
  <p>Found <code>export declare function httpFactory(xhrBackend: XHRBackend, requestOptions: RequestOptions): Http;</code> in http.d.ts line 163. Maybe it can help.</p>