Have issues ordered initially

[ZooeyMiller]

Currently when the page is first loaded the issues are not ordered in any particular way, it would be nice if they were ordered somehow when the page loads, perhaps by the most recently updated issues, so the user can see those with recent activity on them.

[finnhodgkin]

This is ready to go, I'm just waiting on #237 to be merged so it can be added to both the labelled and unlabelled views.

 unless Map.get(rummage_param["sort"], "field") do
    rummage_param = rummage_param
    |> Map.put("sort", %{"field" => "gh_updated_at.desc"})
  end