Originally the dashboard TS expression ``heroes.slice(1, 5))` had been
written as:
> _heroService.getHeroes().getRange(1, 5)
which is brittle; it fails if there are not enough heroes. Slice
doesn't fail; an equivalent express
ion in Dart is
> _heroService.getHeroes().skip(1).take(4)
This is now used.
Other changes:
- Fix in css (missed TS-side update).
- Ran `dartfmt` on `heroes_component.dart`.
f8e6b5d1f7