Add detachScrollListener in componentDidUpdate

[KimSeongIl]

'react-infinite-scroll' is a good component.
But I think there is an issue.

Call the detachScrollListener function only when 'offset' is less than 'threshold' in the scrollListener function.
So when 'hasMore' changes, the detachScrollListener function is not called.
That's why I think the function detachScrollListener should be called in the componentDidUpdate function as well.

[PierreGUI]

Relates to issue #44
The fix here works but isn't enough. You shouldn't detach/attach event listener for every update, but only after a change of hasMore.
See dantzchan@506138f (from issue discussion).
Cheers

[KimSeongIl]

Ok. Thanks for the reply.