Corrections to annotations for Drum-Taps review

Dennis Berthold suggested some improvements to the annotations for A. S. Hill's "[Review of Drum-Taps]," from the North American Review (January 1867).  I have added information about Sam Weller, the more well-known character from Dickens's The Pickwick Papers, to note 2; adjusted the note about the "Bowery Boys" to reflect the fact that they were more a general type than a political gang; and clarified that Fort Sumter, the subject of note 5, was a military outpost that was occupied by the Confederates throughout the Civil War, rather than an "outpost of Union authority," which the note had previously said.

~ Nikki