v2.1.0

• Use Ember.uuid to generate unique IDs
• Add a Handlebars-less compiler; enable with Ember.ENV.I18N_COMPILE_WITHOUT_HANDLEBARS = true;
• {{t}} helper uses Metamorph tags.
• {{t}} helper: allow turning off the default <span> tag; enable with Ember.FEATURES.I18N_TRANSLATE_HELPER_SPAN = false;