renameColumn function requires the doctrine/dbal

Migrations using `renameColumn` function requires the doctrine/dbal.
Please refer http://laravel.com/docs/4.2/schema#renaming-columns

RenameColumn function being used at 
- https://github.com/cachethq/Cachet/blob/master/app/database/migrations/2014_12_01_121947_AlterTableIncidentsRenameComponentColumn.php