Log when we encounter deadlocks causing restart/retry
Use the ActiveSupport::LogSubscriber pattern

Works around nil-logger scenario and is properly integrated with tagging
and request log flushing.
Default logger is ActiveRecord logger

ActiveRecord::LogSubscriber does this too.
Spec notifications being published by locking extensions
Extract log subscriber for locking extensions
Merge pull request #66 from envato/log-deadlocks

Log when we encounter deadlocks causing restart/retry