Show stats nav and remove beta notices

A tabbed navigation allowing users to navigate to the
stats announcements index from the statistics page was
commented out as a feature-flag.

This reinstates it and removes the beta notices on the
stats announcements pages.

Also renames a couple of mis-named scss modules.
/government/statistics shows filtered index of statistics

Statistics are being extracted from the publications section of the site
to be displayed under /government/statistics. This commit creates a new
statistics controller.

It's more of a smoke-and-mirrors approach; The new StatisticsController
inherits from PublicationsController and gets most of it's functionality
from there.

Some thought was given into whether building a new provider in a similar
pattern to the stats announcements, but we decided that since gds hasn't
decided on what shape this kind of thing should be yet, it would be better
to take a less drastic approach for now.
Statistics show pages live at /gov/statistics/:slug

There wasn't much to do here as the new StatisticsController
already inherited everything it needed to show statistics pubs
from the publications controller.
Configure Sidekiq explicitly

At the moment, the sidekiq.rb initializer gets overridden on deployment
to set the correct redis server. This makes it hard to configure sidekiq
with any other settings. This change allows us to override just the
redis config without bludgeon the rest of the sidekiq config.
Merge pull request #1599 from alphagov/sidekiq-config

Configure Sidekiq explicitly
Wire in Sidekiq worker for scheduled publishing
Unschedule dequeues sidekiq job
WIP get tests green again
Cleanup old scheduled publishing code

Note that jobs will have to be queued for any already scheduled
editions, otherwise they will not get published.
Upgrade sidekiq gem

Latest gem gives more insight and controls for dead jobs via the monitor
interface. Also has better error handling compatibility with things
like Airbrake.

Because of a change in the organisation of code in the gem, we now need
to require the file that defines Sidekiq::ScheduledSet.
Add test coverage around scheduled publishing

This was not previously covered by any cucumber scenarios
Use a separate queue for scheduled publishing jobs.

This queue gets a high priority to ensure scheduled publishing jobs are
dealt with sooner rather than later.
Configure sidekiq error handling

Sidekiq 3 removed automatic error handling so we explicitly set it up
here.
Helper methods for checking scheduled jobs

Useful for debugging the current state of the queued jobs.
Change the warning text on statistics announcements

Editors are posting the wrong documents as statistics announcements. This change is to the warning text on the Statistics Announcements page.
Merge pull request #1600 from alphagov/statistics-announcements-warning-text

Change the warning text on statistics announcements
Reduce sidekiq workers per box

This brings whitehall into line with the number of workers on other
apps. It also will help prevent us DDOS-ing transitioning servers during
importing of large numbers of documents/attachments
Merge pull request #1602 from alphagov/reduce-sidekiq-workers

Reduce sidekiq workers per box
Prevent sidekiq tests stomping on real queue

For those tests where we actually need to hit redis for real, we
configure sidekiq to use a separate test namespace, otherwise we'll
stomp over development mode jobs.
Remove the remaining alternate top tasks

The last department are being migrated onto the new style services and
information links. This feature is no longer needed so remove it and all
the related styles to go along with it.