Add a cron job to reindex the closing consultations

Fixes https://www.pivotaltracker.com/story/show/56618324

Including a data migration to go back a month and reindex the closed
consultations, this issue would have only been present since we now use
the ES data to display the consultations and closing is not a
pusblishing state, but derived from the closing_on date.
Move rake task to 1:30am

So not to conflic with export:redirector_mappings which is a heavy task
Merge pull request #835 from alphagov/56618324-closed-consultaiton-stale

Add a cron job to reindex the closing consultations

https://www.pivotaltracker.com/story/show/56618324