Prune operation

[icecrime]

Finish the prune operation, which should be capable of:

• Pinging the original author for items which have shown no activity for a specified amount of time.
• Warning the original author that the item will be closed unless it shows activity under a specified amount of time.
• Close the item after the warning has been issued.

[vieux]

I don't think it's specific to this operation, but it looks like the filtering on issues doesn't work correctly.

I get messages like

INFO[0002] Execute close action on issue #1668 (last commented on 2017-03-10T16:42:36Z) dry_run=true item_num=1668 item_type=issue repository=docker/libnetwork

and as you can see it's a PR.