title: viewWillAppear is not called when add child controller to table view cell
body: <p>When I add child view controller to table view cell, it looks like <strong>viewWillAppear</strong> for child view controller is not called, only <strong>viewDidAppear</strong>.</p>
  
  <p>Table View Controller method:</p>
  
  <pre><code>override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -&gt; UITableViewCell
  {
      let cell = tableView.dequeueReusableCellWithIdentifier("ShopInfoTableViewCell", forIndexPath: indexPath) as! ShopInfoTableViewCell
      self.addChildViewController(self.shopInfoViewController, toView: cell.containerView)
      return cell
  }
  </code></pre>
  
  <p>View Controller category method:</p>
  
  <pre><code>- (void)addChildViewController:(UIViewController *)childController toView:(UIView *)view
  {
      [self addChildViewController:childController];
      [view addSubview:childController.view];
      [childController didMoveToParentViewController:self];
  
      [childController.view mas_makeConstraints:^(MASConstraintMaker *make) {
          make.top.equalTo(view.mas_top);
          make.bottom.equalTo(view.mas_bottom);
          make.left.equalTo(view.mas_left);
          make.right.equalTo(view.mas_right);
      }];
  }
  </code></pre>
  
  <p>Any ideas why it happen?</p>