[angular] Observable.of is not a function

My silly mistake was that I forgot to add /add when requiring the observable.

Was:

import { Observable } from 'rxjs/Observable';
import 'rxjs/observable/of';

Which visually looks OK becasue rxjs/observable/of file, in fact, exists.

Should be:

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';