adds i18n support discussed in #99

I added Ember.EasyForm.eachTranslatedAttribute to utilities (copy paste from [ember-i18n](https://github.com/jamesarosen/ember-i18n/blob/master/lib/i18n.js#L56)). As soon as @jamesarosen exposes the function via Ember.I18n.eachTranslatedAttribute (jamesarosen/ember-i18n#86) we can remove it from utilities.

I stubed Ember.I18n.t in the test and let it humanize the key and hit the 200th test!