Reimplement Sidekiq worker

This better integrates various Sidekiq features into AJ jobs.

Things like the JID will be set as expected and the user can use `sidekiq_options` in AJ::Base subclasses as usual to configure various features.
Adds backburner adapter
Remove all Sidekiq-specific stuff from job, enable retries by default
Have Sneakers adapter take queue_name into account.
Merge pull request #38 from mperham/rework_sidekiq

Reimplement Sidekiq adapter
Reformat the logging line and ensure we are logging the serialized args
Styling
Merge pull request #44 from DouweM/patch-1

Have Sneakers adapter take queue_name into account.
Merge pull request #43 from mytrile/master

Adding backburner(beanstalks client) adapter
Silence logger
Merge pull request #48 from seuros/master

Silence logger
merge master