For now, mount up resque-web at /outpost/resque

Require a logged-in user who is a superuser.
Fix Resque namespace setup

To get a properly-namespaced Resque, the `redis` value passed in needs to be
in the form of `(host):(port)/(namespace)`. You're not allowed to put in a
database. The initializer will take care of the namespace part, so just set
`(host):(port)` in your config.
Add indexing on content updates

* Updates to content that includes the `Model::Searchable` concern will
  enqueue a `Job::Indexer` that will create / update / delete the indexed
  content as-appropriate. Takes care of both the model index (for Outpost)
  and the article content index.
* Add `scprv4:index_all_articles` rake task. Useful during initialization of
  new environments