The Boston Celtics playoff flameout will very clearly be a sore subject in Boston for a little while, but there are still a lot of important things that happened during the regular season that should be celebrated.  Among them is the development of rookie Hugo Gonzalez , who had a big impact on many games during the regular season and finished just behind Jaylen Brown in cumulative +/- this season at +246. Gonzalez has been a high-energy guy who plays as hard as anyone, crashes the glass, makes hustle plays, and is as competitive as anyone on the team. His instincts hint a very bright NBA future , something Brad Stevens seems to see as well.  “Hugo has had a great rookie year and I think is a critical part of us moving forward,” Stevens said at his end-of-season press conference Monday morning. “His athleticism can beat the moment in the big games. That's a real thing. You can see it, you know it. His strength is off the charts.…