Create Sidekiq Worker for Emailing Tax Warnings

[apoltieva]

As a user, I want to be warned when the deadlines for my cars' taxes are coming up. Steps:

• create a Sidekiq worker https://github.com/mperham/sidekiq that would
  • fetch all the taxes for all the users that are due in the next 2 weeks
  • mail users about their upcoming taxes
• make the worker periodic https://github.com/ondrejbartas/sidekiq-cron