v2.2.0

• The {{t}} helper now warns if passed an unquoted key argument. It still uses unquoted arguments as string literals, but this behavior will change in the next major release.
• Removed deprecation warning for those who've opted in to I18N_COMPILE_WITHOUT_HANDLEBARS
• Fixed a typo in the warning message for I18N_COMPILE_WITHOUT_HANDLEBARS
• Remove check for Ember.I18n.fire as that was only necessary on Ember 0.9, which this library no longer supports.
• Don't warn on missing translations. Clients that want to be notified can subscribe to the missing event on Ember.I18n.
• compileWithHandlebars uses saved-off warn helper (which uses Ember.Logger.warn rather than Ember.warn).
• Run separate Travis builds for each dependency set.
• Add Sinon as a test dependency and use its spies in specs.