At least 80 people were killed inside the concert venue Friday
                                
                                
                                    (Newser) -
                                    As mourners lined up to leave flowers and candles outside Paris' Bataclan, where  at least 80 people were killed  during a terrorist attack Friday, a solitary man played John Lennon's Imagine on a piano, the  Guardian  reports. According to the  BBC , a small crowd gathered to listen to Davide...