title: "ERROR TypeError: Object(...) is not a function" using AngularFirestore and firebase
body: <p>I want to use firebase and angularfire2 in my app, first of all, I installed them, and for the declarations:</p>
  
  <p>in environment.ts</p>
  
  <pre><code>export const environment = {
      production: false,
      firebase: {
      apiKey: 'sfsdfdsff',
      authDomain: 'sfsdfdf',
      databaseURL: 'https://ng-sfsdfsf.firebaseio.com',
      projectId: 'ng-fitnesssfsdfdsf',
      storageBucket: 'ng-fsdfsdfsfdecff5.appspot.com',
     messagingSenderId: '21331323'
     }
    };
  </code></pre>
  
  <p>in app.module.ts, imports:</p>
  
  <pre><code>AngularFireModule.initializeApp(environment.firebase),
  AngularFirestoreModule
  </code></pre>
  
  <p>in the component where  want to get my data:</p>
  
  <pre><code>import { AngularFirestore } from 'angularfire2/firestore';
  </code></pre>
  
  <p>until this moment I have not an error, but when I want to declare my variable in the constructor to use it:</p>
  
  <pre><code>constructor(private trainingService: TrainingService, private 
  db:AngularFirestore) { }
  </code></pre>
  
  <p>I have an error:</p>
  
  <pre><code>ERROR TypeError: Object(...) is not a function
  at eval (firestore.js:28)
  at ZoneDelegate.invoke (zone.js:388)
  at Zone.run (zone.js:138)
  </code></pre>
  
  <p>In my package.json:</p>
  
  <pre><code>"angularfire2": "^5.0.0-rc.8.0",
  "core-js": "^2.4.1",
  "firebase": "^5.0.2",
  </code></pre>
  
  <p>and I don't know why?</p>
  
  <p>thanks for your help</p>