NASHVILLE, Tennessee (Reuters) - Rising stars Little Big Town and Thompson Square were among early winners at the Country Music Association awards on Thursday, on a night that mixed old stars and newcomers. Alabama quartet Little Big Town scooped up its first CMA award, winning single of the year for the hit record "Pontoon," while husband-and-wife team Thompson Square took home the prize for best vocal duo. "This is one of the coolest things we have ever experienced," said Keifer Thompson, accepting the award for the duo early in the televised ceremony from Nashville. ...