“Firefly” Felled by the Fox. Continuing the success afforded by his back-to-back TV successes “Buffy the Vampire Slayer” (1997-2003) and “Angel” (1999-2004), writer/producer/director Joss Whedon (currently of Disney/Marvel “Avengers” cinematic fame) created, along with “Angel” partner Tim Minear (“American Horror Story”), a short-lived TV series (2002-2003) that could be described in broad terms as ‘Han…