ThreadSubscription.java:39-42: Add properties subscribed (boolean),...

The puzzle `913-504d1bd2` in [`src/main/java/com/jcabi/github/ThreadSubscription.java`](https://github.com/jcabi/jcabi-github/blob/master/src/main/java/com/jcabi/github/ThreadSubscription.java) (lines 39-42) has to be resolved: Add properties subscribed (boolean), ignored (boolean), createdAt (Date), url (String), threadUrl (String) as shown in section "Response" at https://developer.github.com/v3/activity/notifications/#response-6 .

The puzzle was created by Dmitri Pisarenko on 22-Jan-15.

Estimate: 30 minutes, role: IMP.

If you have any technical questions, don't ask me, submit new tickets instead. The task will be "done" when the problem is fixed and the text of the puzzle is removed from the source code. Here is more about [PDD](http://www.yegor256.com/2009/03/04/pdd.html).