Fix github org-pulls command.
Increase github org-pulls issues fetched by the API.

The more issues returned by the API the more org-pulls can be shown by
the script; currently no pagination of the GitHub API is implemented,
so the number of open pull requests will be however many are found in
the first 100 open issues returned by the API.
Merge pull request #1569 from tonymilne/master

Fix github org-pulls command.