title: Remove a value from Firebase Array
body: <p>I have a array in firebase created using the push() function.</p>
  
  <p>I am trying to remove a specific value in that array.</p>
  
  <pre><code>var arr = $firebaseArray(ref.child('invoices').child('pending').child(coId));
  
  arr.$loaded().then(function(){
      var index = arr.$getRecord(invoiceId);
      arr.$remove(index);
  })
  </code></pre>
  
  <p>However, this is not working.  I keep getting -1 for the var index. If there is an easier way to remove a value, with or without angularFire, I would be open to it. </p>
  
  <p>Thanks! </p>