Avril Lavigne and Mod Sun have established themselves as one of music's newest power couples, and celebrated a very special milestone to that effect.MORE: Avril Lavigne shares major celebratory clip from incredible Malibu homeMod shared a clip on his Instagram Stories where he revealed that he and his girlfriend were spending time together to mark their one year anniversary.He and Avril adoringly cuddled up against each other in the dark clip as he kissed her head and she then nuzzled up to