Um, what do we have here?!?! The rumor mill is in overdrive after Zoë Kravitz stepped out in London flashing a very eye-catching piece of jewelry on THAT finger while locking lips with her beau, Harry Styles. Yes, you read that right. A ring. On that finger. And not just any ring, either. We're talking a sparkler big enough to make even the most seasoned celebrity watchers do a double take! Related: Harry & Zoë DON'T Share A Bed Amid Months-Long Relationship & Multiple Trips Together?! The photos, which hit the internet in waves on Sunday and again on Tuesday, show the ultra-cool actress-sin...