Conflict with array-selector when updating an item in firebase  #81

When an item in firebase get's updated the components call the following code. The given code will call splices on the array which causes any selected item to be deselected.

_onFirebaseChildChanged: function(event) {
this._applyRemoteDataChange(function() {
var value = this._valueFromSnapshot(event.detail.childSnapshot);
var oldValue = this._valueMap[value.firebaseKey];

      if (!oldValue) {
        this._error('Received firebase-child-changed event for unknown child "' + value.__firebaseKey__ + '"');
        return;
      }

      this._valueMap[oldValue.__firebaseKey__] = null;
      this._valueMap[value.__firebaseKey__] = value;
      this.splice('data', this.data.indexOf(oldValue), 1, value);
    });
  },