vnode.state in attribute lifecycle methods should be documented

[dead-claudia]

In components, it's already documented to be equal to the component instance. In attributes, it's not even documented to start. In the source, it's already well-tested in the case of DOM vnodes, but not component vnodes or fragments AFAIK. The current behavior is this:

• DOM vnodes: vnode.state = {}
• Fragments: vnode.state = {}
• Components: vnode.state = componentState (same as what's in components)

[barneycarroll]

Might be worth showing how eg fragments can be used to do simple 3rd party / DOM effects setup / teardown without requiring component declaration.