related: allow posting on issues not created in the last two days

[zpavlinovic]

Currently, gaby related issues agent will contribute a post only if the corresponding issue was created in the last two days. If gaby goes offline for, say, three days, the poster will skip one day's worth of issues. This limit is imposed as a way of not posting to ancient issues. Few alternatives:

1. Set a limit to a fixed time in the past. Pros: simple. Cons: will likely depend on github project and the user.
2. Do not have a time limit at all, yet always post for open issues. Pros: simple and should not be dependent on the project or user. Cons: authors of stale issues might get annoyed.