Lock redis library to an earlier version
Lock redis library to an earlier version

Redis 3.3.8 produced `AttributeError: 'unicode' object has no attribute
'iteritems'` for me; let's see if the previous version helps.

ministryofjustice/laa-legal-adviser-api,ministryofjustice/laa-legal-adviser-api,ministryofjustice/laa-legal-adviser-api