Bugfix for unmounting component with OverlayMixin

Should not try to .removeChild when the target div has not been created yet, browser throws NotFoundError.
Add test to Button to show that it transfers props, allowing additional classes to be added to element

Add test to Panel to show that it transfers props, allowing additional classes to be added to element, and implement

Strengthen tests slightly to make sure not replacing existing class

remove duplicate test, remove blank lines
Merge pull request #114 from time4tea/master

PR to fix additional className for Panel Issue #101
Pass `bsSize` to the `modal-dialog`. Fixes #115
Merge pull request #116 from react-bootstrap/bugfix/modal-size

Pass `bsSize` to the `modal-dialog`. Fixes #115
Fix corners on vertical `ButtonGroup` #117
Typo
Merge pull request #119 from davidbgk/patch-1

Typo
ie8 test page
Use React's EventListener in DropdownStateMixin

Works with ie8
Fix overriding of `bsStyle` on `Panel` by `PanelGroup`
Merge pull request #121 from stereosteve/ie8

IE8 test page + fix DropdownStateMixin
ie8: Modal uses EventListener
ie8: fix DropdownStateMixin.unbindRootCloseHandlers

Empty the array of event listeners when unbinding.
Merge pull request #123 from stereosteve/ie8

IE8: modal
Pass `bsStyle` from `TabbedArea` to `Nav`

also fixes some whitespaces in TabbedArea test
Merge pull request #126 from brainary/tabbedarea-bsstyle

Pass `bsStyle` from `TabbedArea` to `Nav`
Merge pull request #122 from react-bootstrap/bugfix/panel-bsstyle

Fix overriding of `bsStyle` on `Panel` by `PanelGroup`
Merge pull request #118 from react-bootstrap/bugfix/button-group-vertical

Fix corners on vertical `ButtonGroup` #117
Carousel refactor

This change included general logic cleanup as well as the following
changes:

Fixed issues
* Clear any timers on `componentWillUnmount` or null any async actions
via `this.isMounted` which would cause set states after the component
has been unmounted, resolves #112.
* Prevent default on `next` and `prev` callbacks which stops hashes being
set to the url.
* Clear auto slide interval timer on manual change to stop multiple
timers being set.

Added functionality
* Added `onSlideEnd` prop - useful for queuing state changes.
* Added basic unit tests.