Fixed doc description
Fixed doc description

Closes https://github.com/PistonDevelopers/piston/issues/471

bvssvni/piston,mitchmindtree/piston,PistonDevelopers/piston,KevinFrans3/piston,PistonDevelopers/piston,getynge/piston,caldwell/piston,bvssvni/piston,oldmanmike/piston,Potpourri/piston,tempbottle/piston,axelmagn/piston,placrosse/piston