Fixed bug with row->setClass in column->manipulateRenderCell

I had this script.

```php
$lastNumber= new TextColumn(array('id' => 'lastNumber', 'title' => 'Last number'));
$lastNumber->manipulateRenderCell(function($value, $row, $router)
{
	/** @var $row \APY\DataGridBundle\Grid\Row */
	/** @var $router \Symfony\Bundle\FrameworkBundle\Routing\Router */
	if($value < 1)
	{
		$row->setClass('A');
	}
	return $value;
});
$grid->addColumn($lastNumber);
```

And then I see that the `<tr>` has the same class then before...
After this merge request the manipulateRenderCell could manipulate the color and class of the row.

I think that would be nice :+1: