Expand / collapse stateful higher-order component

[vladimirivanoviliev]

Implement build-in expand / collapse stateful / stateless higher-order component which:

Should expect:

• items hierarchy as flat array of objects. Example:

[{id:1, title: "some title", parentId: null}, {id:2, title: "other title", parentId: 1}]

Should handle:

• to listen on "onSelect" event of the child component and make changes to it's state (toggle expand / collapse state of items)
• on props change to merge the received data with current state

Should trigger:

• onChange event to notify high-order component about the changed items

Example implementation is available here: PanelBarToggle

This feature is related to: #11