Added sidekiq service management from the capistrano script.

When the app is started, stopped or restarted, the sidekiq service will as well.

It is required that the "feedbunch" user has passwordless sudo enabled to manage the sidekiq service in the background server. See these guides:

https://www.digitalocean.com/community/tutorials/how-to-edit-the-sudoers-file-on-ubuntu-and-centos
http://stackoverflow.com/questions/21830644/non-privileged-non-root-user-to-start-or-restart-webserver-server-such-as-ngin