title: Can not push data to google firebase with react js
body: <p>I am using ReactJS (with ECMA6) and Google Firebase@3.0.3 and ReactFire@0.4.0 as middleware, but I can not get to push data to the firebase</p>
  
  <hr>
  
  <pre><code>import ReactFire from 'reactfire';
  import Firebase from 'firebase';
  let config = {
    apiKey: "apiKey",
    authDomain: "projectId.firebaseapp.com",
    databaseURL: "https://databaseName.firebaseio.com"
  };
  Firebase.initializeApp(config);
  </code></pre>
  
  <hr>
  
  <p>when it comes to this: </p>
  
  <pre><code>componentWillMount() {
      let ref = Firebase.database().ref('/items');
      ReactFire.bindAsObject(ref, 'items');
    }
  </code></pre>
  
  <p>it gives me '<strong>firebaseRef.ref is not a function</strong>'</p>
  
  <hr>