Add database rollback API endpoint
Rollbacks API endpoint exposes multiple rollback jobs

Switched from single resource to multiple resource route and actions
Rename Rollback#rollback_to to Rollback#date for clarity

Causes unnecessary issues in tariff admin app
Make sure Rollback#date is a valid date

Refactor Rollback create response so it returns 201 (Created) and
presentation of Rollback job
Add sidekiq.yml config file
Synchronizer Rollback accepts date argument as Date and String

String has to be parsed to Date in order for Sequel to properly forge a
deletion query. Otherwise we loose data due to incorrect query.
Add Procile for Sidekiq startup

Just as Whitehall does have.
Enable Redis on Travis
Fix sidekiq integration spec

This spec required sidekiq to be run in integration mode as we are
querying real Redis queue for data
Add sidekiq initializer

So that jobs won't clash between projects
Configurable Redis logger (for development)
Use Redis locks to prevent several Rollback workers from clashing

Refactored other instances of lock usage so that they would use Redis
lock as well. We cannot allow using 2 different types of locks because
that would allow update and rollback actions to happen at the same time.
Merge pull request #137 from alphagov/50000203-database-rollback-api-endpoint

50000203 database rollback api endpoint