Ariana Grande's performance of "Tattooed Heart" at the 2013 American Music Awards on Sunday night managed to shock the likes of Lady Gaga, who gave the young songstress a standing ovation. Grande performed the single off her album, "Yours Truly," leading with an a cappella rendition of "Baby I," on the AMAs stage at the Nokia Theatre L.A. Live on Nov. 24. She sang her heart out in a performance MTV News has compared to the Motown vibe of Gladys Knight and the Pips, in front of an audience packed...