“Neighbors” is the next big comedy of the summer season and pretty much exactly what you’d expect from a movie co-starring Seth Rogen and Zac Efron. For a while, it appears to be an insightful comedy about the difficulties of entering the parental stage of life. Mac (Rogen) and Kelly (Rose Byrne) are typical 20-something new parents, attempting to be responsible without completely losing their ability to be spontaneous and fun.