Use ember.debug.js if it exist

`ember.js` is deprecated in favor of `ember.debug.js`
later than Ember.js 1.10.0.beta.1.
* https://github.com/emberjs/ember.js/issues/9830
* https://github.com/emberjs/ember.js/pull/9845
Support ember.debug.js for generator
Merge pull request #403 from tricknotes/ember.debug.js

Use ember.debug.js if it exist