Update dependencies & github actions

[aelkiss]

• Add action to deploy to production & set image for all cronjobs
• Use shared actions from github.com/hathitrust/github_actions
• Enable reporting coverage to simplecov
• Update gems
• Update README to indicate you need to get submodules

[aelkiss]

Note this is using the (unmerged) update to https://github.com/mlibrary/deploy-to-kubernetes that lets us set the image for all cronjobs at once. The corresponding ht_tanka update is https://github.com/hathitrust/ht_tanka/pull/42

[aelkiss]

Agreed.