Fix sidekiq config.

Sidekiq expects symbol keys, whereas the REdis client itself will handle
either.  This was causing sidekiq to run without a namespace.
Merge pull request #184 from alphagov/fix_sidekiq_config

Fix sidekiq config.
Fix scheduled publishing test

the test was not taking into account last dates
of the month, so was selecting an invalid date
for scheduling and hence failing.
Merge pull request #186 from alphagov/make-test-resistant-to-clock-changes

Fix scheduled publishing test