Following his three-day bus tour to promote his economic agenda -- and not to mention the debt limit rancor in Washington before that -- President Obama is finally getting some rest and relaxation. On Thursday, he and his family are heading off to Martha's Vineyard, the island off of Massachusetts. They'll be staying at a 28-acre retreat called Blue Heron Farm for about 10 days. There has been criticism of the president's vacation at this time. But how does the number of vacation days the president has spent compare to his predecessors? CBS Radio's Mark Knoller has kept track of...