The robotics entrepreneur who helped bring the Roomba vacuum into millions of homes is now pursuing a new idea: a plush robotic companion that could one day stand in for a cherished dog or cat, trailing behind you and adjusting to your everyday routines. On Monday, Colin Angle introduced a four-legged prototype of this artificial pet, known as the Familiar. About the size of a bulldog, it features wide, gentle eyes and rounded ears and paws reminiscent of a bear cub. The creature can stretch