Carousel is now responsive and pictures can be viewed on smartphones, tablets, etc. entirely.
Enabled email notifications for cars and passengers.

- Replaced delayed_job by sidekiq, since couldn't test properly.
- Fixed controllers to be able to delete cars and passengers.
- Changed CC'ed emails to leverage GMail aliases.
- Enabled mailers in car and passenger' models.
- Fixed notice in cars' index view.
- Fixed migration by removing arrival time.
- Improved locales.
- Fixed URLs in emails' bodies.
- Harmonized quotes.