:sparkles: tabs components

[bpetetot]

The <Tabs> component will be used in the workbench screen (for props, state...) and the documentation screen (to switch from edit to preview mode)

It's a basic implementation of tabs, that can be used like that :

<Tabs className="myClass">
    <Tab title="props"><Props /></Tab>
    <Tab title="state">Not implemented yet.</Tab>
</Tabs>

The following features are available on the <Tabs> component

• Tabs#defaultKey prop to select a default tab
• Tabs#actions prop to add an action bar on the right of the tabs
• Tab#title prop is a PropTypes.node

And the Tabs, Tab, TabsHeader and TabsActions styles can be overridden.