Added Redmon gem to monitor the Redis instance serving as Rails cache backend.

The Redmon GUI can be accessed at the /redmon path.
Created worker to update Redmon stats every minute.

It is a Sidekiq worker, scheduled with Sidetiq to run every minute. It collects stats from the Redis instance used as Rails cache backend, which can then be visualized with Redmon at the /redmon path.
Allow access to Redmon only to admin users, via the user dropdown menu.
Fixed bug in worker (missing require statement).
Require Sidekiq >= 3.2.5

Version 3.2.4 and below have issues when shutting down. There's also mention in the bugreport of a memory leak, but I haven't been able to confirm it in this app.

The fix is to add a >=3.2.5 condition in the Gemfile. That is the first version that fixes this issue, or at least works around it. It seems to be some problem with recent Celluloid versions, or a race condition that only manifests in recent Celluloid versions. Version 3.2.5 of Sidekiq fixes version 0.15.2 of Celluloid as a dependency, which seems to make the problem go away for now.

I don't directly include Celluloid, so I'm not too worried about staying with older versions as long as Sidekiq works.

For more about this bug:

https://github.com/celluloid/celluloid/issues/457
Removed code that decided whether to apply a CSS class that added padding-top to the body to leave enough space for the navbar.

It is not necessary to check if the current user is authenticated to apply the class. There are views which only an authenticated user can reach, and it's safe to always use this class (the navbar is always visible when a user is authenticated). Conversely there are views which can only be reached by unauthenticated users; it's safe never using the class in those, because the navbar is never visible for unauthenticated users.
Added rake task and capistrano task for clearing the Rails cache.

The rake task can be invoked with "rake rails_cache:clear" to clear the cache in the local machine.

The capistrano task can be invoked with "cap production redis_cache:clear" to remotely clear the cache in the production environment. This actually invokes remotely the above rake task.

The idea is to invoke this if the server starts serving stale content, because of changes to views that are not picked by the caching system or any other reason.
Removed navbar fragment from those views in which the navbar never actually appears.

Removed from navbar fragment the validation that checked that the current user was logged in. Those views that show the navbar can only be reached by authenticated users, so that validation is now useless.
Simplified user menu fragment.

If the user is displayed the menu, we can be sure that the user is authenticated. It is not necessary to wrap the frament in an "if" that validatesthat the user is authenticated.
Added caching statements for the application layout and associated fragments.

Where appropiate, different cached versions are stored for each locale, so that user content is served in the correct locale. Also in the case of the user menu two different versions are cached, one for admin users and another for regular users.