started bootstrap docs

docs/guide/bootstrap-widgets.md

-Twitter Bootstrap widgets
-=========================
+Bootstrap widgets
+=================
 
-Overview
---------
+Yii includes support of [Bootstrap 3](http://getbootstrap.com/) markup and components framework out of the box. It is an
+excellent framework that allows you to speed up development a lot.
 
+Bootstrap is generally about two parts:
+
+- Basics such as grid system, typography, helper classes and responsive utilities.
+- Ready to use components such as menus, pagination, modal boxes, tabs etc.
+
+Basics
+------
+
+Yii doesn't wrap bootstrap basics into PHP code since HTML is very simple by itself in this case. You can find details
+about using the basics at [bootstrap documentation website](http://getbootstrap.com/css/). Still Yii provides a
+convenient way to include bootstrap assets in your pages with a single line added to `AppAsset.php` located in your
+`config` directory:
+
+```php
+public $depends = array(
+	'yii\web\YiiAsset',
+	'yii\bootstrap\BootstrapAsset', // this line
+);
+```
+
+Using bootstrap through Yii asset manager allows you to combine and minimize its resources with your own ones when
+needed.
+
+Yii widgets
+-----------
+
+Most complex bootstrap components are wrapped into Yii widgets to allow more robust syntax and integrate with
+framework features. All widgets belong to `\yii\bootstrap` namespace. Let's review these.
+
+### Alert
+
+### Button
+
+### ButtonDropdown
+
+### ButtonGroup
+
+### Carousel
+
+### Collapse
+
+### Dropdown
+
+### Modal
+
+### Nav
+
+### NavBar
+
+### Progress
+
+### Tabs
+
+### Typeahead