utilities/gitlab_recurring_issue#8: Github Support

It might be worth looking at how easily we could add Github support to this too.

We could then provide a target within the ticket (with the default being gitlab)

gitlab:
  url: http://gitlab.example.com
github:
  token: "foobarsed"
tickets:
      - title: "Test nth sunday"
        target: github
        active: true
        schedule:
            nth:
                n: 2
                weekday: Sun
        project: bentasker/updates
        description: "This is a test issue"
        assignee: ben
        labels: ["task", "foobar"]

Potentially we could even be a bit more advanced and allow a template to support both - creating the same ticket in Github and Gitlab.