Update CHANGES.md with info on Celluloid#async
Update CHANGES.md with info on Celluloid#async

olleolleolle/celluloid,sideci-sample/sideci-sample-celluloid,davydovanton/celluloid,tarcieri/celluloid,dilumn/celluloid,TiagoCardoso1983/celluloid,celluloid/celluloid,marshall-lee/celluloid,seuros/celluloid,mehta/celluloid,jstoja/celluloid,jasonm23/celluloid,kenichi/celluloid