Update app-version.js
Update app-version.js

the app/ dir of an addon must be written ES3/ES5 safe with the exception of ES6 Module syntax.

We will soon make babel mandatory which will make this a non-problem, but until then.
cibernox/ember-cli-app-version,joliss/ember-cli-app-version,philipbjorge/ember-cli-app-version,philipbjorge/ember-cli-app-version,joliss/ember-cli-app-version,cibernox/ember-cli-app-version,embersherpa/ember-cli-app-version,embersherpa/ember-cli-app-version