Third time’s the charm?  Following the shocking news that Glen Mazzara would be stepping down as showrunner on AMC’s hit drama series The Walking Dead, TV Line now reports that supervising producer Scott Gimple has been tapped as the replacement.  Gimple will mark the third showrunner on the 3-season-old series, as original creator/showrunner Frank Darabont was forced out halfway through the show’s second season.  Hit the jump for more details.