PARIS (Reuters) – The Rolling Stones performed an energetic warm-up gig in Paris on Thursday for a few hundred fans after announcing on Twitter that tickets would go on sale for 15 euros ($19.45) just hours in advance. "I can't believe we're all still standing up, you'd think by now one or two of us would be sitting down, but we're not," lead singer Mick Jagger, 69, told fans at the Trabendo, a 700-capacity venue in northern Paris, during the 75 minute surprise show. Fans said the small space created an optimal setting for the show which kicked off with "Route 66" and ended with "Brown Sugar". …