Song is out May 4 instead of May 5 With the Princess of Pop by her side, Iggy Azalea is making a second run at the song-of-summer throne. Almost a year after her ubiquitous Fancy with Charli XCX began its seven-week reign atop the Billboard Hot 100 — Azalea's first in a string of female-fueled hits with Ariana Grande, Rita Ora, Jennifer Lopez and Jennifer Hudson — the Aussie rapper joins Britney Spears for the new single Pretty Girls, out May 4. "You definitely need a partner to sing (it wi