Adding functionality to find a job by job id and delete a job by job id from a SortedSet

Functionality to find and delete Sidekiq jobs by the job id.  @mperham, I think this is more in line with what you were thinking.

Example usage:

**Finding and Deleting Job by ID**

    Sidekiq::SortedSet.new('schedule').find_job_by_id('2eef6b752dab8a4c89a7aa19')
    => #<Sidekiq::SortedEntry:0x007fd5a910e858 @value=".....> 

    Sidekiq::SortedSet.new('schedule').delete_job_by_id('2eef6b752dab8a4c89a7aa19')
    => true 

**Finding and Deleting Invalid Job ID**

    Sidekiq::SortedSet.new('schedule').find_job_by_id('2eef6b752dab8a4c89a7aa19')
    => nil 

    Sidekiq::SortedSet.new('schedule').delete_job_by_id('2eef6b752dab8a4c89a7aa19')
    => nil 

**Or you can use it on ScheduledSet to access the scheduled queue directly** 

    Sidekiq::ScheduledSet.new.find_job_by_id('719a82379213ccab7551bc7e')
    => #<Sidekiq::SortedEntry:0x007fd5a928f6a0 @value=".....>
 
    Sidekiq::ScheduledSet.new.delete_job_by_id('719a82379213ccab7551bc7e')
    => true
 
    Sidekiq::ScheduledSet.new.find_job_by_id('719a82379213ccab7551bc7e')
    => nil 

    Sidekiq::ScheduledSet.new.delete_job_by_id('719a82379213ccab7551bc7e')
    => nil