corrected grunt version in readme
corrected grunt version in readme

cgvarela/assemble,assemble/assemble,assemble/grunt-assemble,a0000001/test,valentinvieriu/assemble,cgvarela/assemble,assemble/assemble,davidwickman/assemble,xetryj/assemble,edrohler/assemble,edrohler/assemble,davidwickman/assemble,avr/assemble,makotot/assemble,xetryj/assemble,assemble/grunt-assemble,valentinvieriu/assemble