In Yii 2.0, the yii widgets that use Twitter Bootstrap CSS & JS directly, are part of the yii2-bootstrap extension, starting with yii/bootstrap namespace. For customizing bootstrap extension specific widget assets, you could configure your own assets (CSS/JS) using the new Yii Asset Manager in your Yii Config file. Something like:
This tutorial describes how to connect to a remote service via tunnel when only most basic software is available on the remote server. It is not directly related to Yii. It could be hovewer useful for web developers working with shared hosting sites with limited access.