By Alexis Schlesinger Editorial Staff Courtesy of Alexis Schlesinger Tiberius, the alternative-indie-country band and beloved pillar of the Boston music scene, celebrated their fifth album, “Troubadour,” with a beautiful show in Somerville on Nov. 15. Tiberius consists of lead vocalist Brendan Wright, bassist Kelvin “KP” Polite, drummer Sam Blumenstiel, pedal steel player Pat King, and recently joined guitarist Colin Boyd. According to Tiberius’ website, the band started ou