fix(core): Observable.throw added to polyfills

Author: Ilya Zolotukhin

src/polyfills.ts

@@ -83,6 +83,7 @@ import 'rxjs/add/operator/pluck';
 import 'rxjs/add/operator/filter';
 import 'rxjs/add/operator/switchMapTo';
 import 'rxjs/add/observable/merge';
+import 'rxjs/add/observable/throw';
 import 'rxjs/add/observable/fromEvent';
 import 'rxjs/add/observable/forkJoin';