Modified README.md for usage of userprefs::vim
Modified README.md for usage of userprefs::vim

TRAINTECH-361 #resolved #time 5m

joshsamuelson/pltraining-userprefs,samuelson/pltraining-userprefs,samuelson/pltraining-userprefs,puppetlabs/pltraining-userprefs,carthik/pltraining-userprefs,carthik/pltraining-userprefs,joshsamuelson/pltraining-userprefs,samuelson/pltraining-userprefs,puppetlabs/pltraining-userprefs