message: fix: Index button is always 'active'
diff: @@ -20,19 +20,24 @@ import { AppState } from './app.service';
  ],
  template: `
  <nav>
  - <a [routerLink]=" ['./'] " routerLinkActive="active">
  + <a [routerLink]=" ['./'] "
  + routerLinkActive="active" [routerLinkActiveOptions]= "{exact: true}">
  Index
  </a>
  - <a [routerLink]=" ['./home'] " routerLinkActive="active">
  + <a [routerLink]=" ['./home'] "
  + routerLinkActive="active" [routerLinkActiveOptions]= "{exact: true}">
  Home
  </a>
  - <a [routerLink]=" ['./detail'] " routerLinkActive="active">
  + <a [routerLink]=" ['./detail'] "
  + routerLinkActive="active" [routerLinkActiveOptions]= "{exact: true}">
  Detail
  </a>
  - <a [routerLink]=" ['./barrel'] " routerLinkActive="active">
  + <a [routerLink]=" ['./barrel'] "
  + routerLinkActive="active" [routerLinkActiveOptions]= "{exact: true}">
  Barrel
  </a>
  - <a [routerLink]=" ['./about'] " routerLinkActive="active">
  + <a [routerLink]=" ['./about'] "
  + routerLinkActive="active" [routerLinkActiveOptions]= "{exact: true}">
  About
  </a>
  </nav>
  