ensure we npm install on appveyor
ensure we npm install on appveyor

ef4/broccoli-sourcemap-concat,ef4/broccoli-sourcemap-concat,broccolijs/broccoli-concat,rlivsey/broccoli-concat,broccolijs/broccoli-concat,ember-cli/broccoli-concat,rlivsey/broccoli-concat,ember-cli/broccoli-concat