Early on in the development of the digitally animated, theater-bound film “Ruby Gillman, Teenage Kraken,” the story is said to have centered more on the titular character’s family, all of whom are secretly krakens. The pivot to an emphasis on Ruby — a 16-year-old high school student having to hide the fact she is, in fact, of the sea while navigating the highs and lows of adolescence — was a wise one.