Demi Lovato brought on the nostalgia in a note to childhood co-star — and these days, fellow pop star — Selena Gomez. She sent a tweet of congratulations to Gomez about her new single last Friday, joking, “We’ve come a long way since our Barney days.” “Loving your new song Fetish,” Lovato wrote. The friendly sentiment was reciprocated by Gomez, who…… MORE