app.module.ts

// ... other imports
import { Http, RequestOptions } from '@angular/http';
import { AuthHttp, AuthConfig } from 'angular2-jwt';
import { TaskListService } from './task-list/task-list.service';

// creates a factory to AuthHttp
export function authHttpFactory(http: Http, options: RequestOptions) {
  return new AuthHttp(new AuthConfig(), http, options);
}

@NgModule({
    // ... other properties
    providers: [
      AuthService,
      TaskListService, // adds new service
      {
        provide: AuthHttp,
        useFactory: authHttpFactory, // defines how to provide AuthHttp
        deps: [ Http, RequestOptions ]
      }
    ],
    bootstrap: [AppComponent]
})