Gruntfile.js: skip the cdnify task if we are on CI.
Gruntfile.js: skip the cdnify task if we are on CI.

mpc-hc/mpc-hc.org,mpc-hc/mpc-hc.org,FeodorFitsner/mpc-hc.org,mpc-hc/mpc-hc.org,FeodorFitsner/mpc-hc.org,FeodorFitsner/mpc-hc.org