By Ayenat Mersie KIGALI (Reuters) -The newly-expanded Commonwealth made broad commitments on Saturday to address climate change and boost trade, concluding a summit aimed at shoring up the relevance of a group that evolved from the British empire. The club, whose 56 members range from India to the tiny Pacific island nation of Nauru, covers some 2.5 billion people or about one-third of the world’s population. It presents itself as a network for cooperation, but critics say it needs to carve out a more concrete role and be less of a talking shop. The week-long summit in Rwanda’s capital Kigali …