Periphery, “Periphery IV: Hail Stan.” Since Washington, D.C.’s Periphery helped spearhead a Meshuggah-worshiping tech-metal offshoot, what’s kept the band relevant hasn’t been  the polyrhythms, but the songwriting. The band’s hyper-syncopated breakdowns have proven an unlikely partner for sticky vocal melodies and adventurous playing. Now on its very own label,…