* Add index and show pages for series
* Address code review
* Use `id` instead of `slug` to get collections
* Extract `collection_link` into the application helper
* Only count published articles
* Get rid of the `collection_link_class` method
* Add tests
* Fix test
* Use `**kwargs` instead of `options = {}`
* Use pick instead of pluck first
* Use touch_all instead of update_all
* Use destroy_by instead of where.destroy_all
* Use scopes
* Fix db:seed:replant
* Remove ActiveSupport::Cache::RedisCacheStore expires_in cache
