There was something different in the air today at the 20th annual Boston Freedom Rally at the Boston Common. And it wasn’t just the clouds of pungent marijuana smoke. It was the first time the rally organized by the Massachusetts Cannabis Reform Coalition had been held since voters passed Proposition 2 last November, which decriminalized possession of small amounts of marijuana. The changed law gave attendees reason to celebrate and a better chance of not getting arrested -- a scenario organizers say is a welcome change for the event, which has caused controversy over the years, including many arrests and...