• Added note methods to Minion::Job and Minion::Backend::Pg.
  
• Added notes option to enqueue methods in Minion and Minion::Backend::Pg.
  
• Added notes field to info method in Minion::Job and job_info method in Minion::Backend::Pg.
  
• Improved performance of stats and lock methods in Minion::Backend::Pg with a new index and other optimizations.
  (depesz)
  
• Improved benchmark script to be more consistent. (depesz)