Block concat 2.0.0 to prevent dependency error
Block concat 2.0.0 to prevent dependency error

concat-2.0.0 is causing negative dependency errors. Depend on `< 2.0.0`
in the classroom until that's sorted out, on the advice of @mhaskel

carthik/pltraining-classroom,spidersddd/pltraining-classroom,carthik/pltraining-classroom,puppetlabs/pltraining-classroom,binford2k/pltraining-classroom,natemccurdy/pltraining-classroom,natemccurdy/pltraining-classroom,klynton/pltraining-classroom,dylanratcliffe/pltraining-classroom,klynton/pltraining-classroom,dylanratcliffe/pltraining-classroom,joshsamuelson/pltraining-classroom,samuelson/pltraining-classroom,puppetlabs/pltraining-classroom,puppetlabs/pltraining-classroom,binford2k/pltraining-classroom,klynton/pltraining-classroom,joshsamuelson/pltraining-classroom,fnaard/pltraining-classroom,dylanratcliffe/pltraining-classroom,samuelson/pltraining-classroom,joshsamuelson/pltraining-classroom,spidersddd/pltraining-classroom,natemccurdy/pltraining-classroom,carthik/pltraining-classroom,samuelson/pltraining-classroom,binford2k/pltraining-classroom,spidersddd/pltraining-classroom,fnaard/pltraining-classroom,fnaard/pltraining-classroom