Expand intro in README
Expand intro in README

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