When Rachel Raney and David Murray set out to create a film on suburban sprawl and the rise of “McTowns,” they never imagined the stories they’d find. The result is Livemore, part documentary, part fairytale, part mystery, and mostly comedy: a portrait of a formerly bucolic suburb threatened by rapid growth and change and the handful of eccentric old-timers struggling to hold on to what makes their piece of small-town America unique.