Add MailPoet.I18n for basic translation handling, removed MailPoetI18n

assets/js/src/i18n.js

@@ -0,0 +1,25 @@
+define('i18n',
+  [
+    'mailpoet',
+    'underscore',
+  ], function(
+    MailPoet,
+    _
+) {
+  'use strict';
+
+  var translations = {};
+
+  MailPoet.I18n = {
+    add: function(key, value) {
+      translations[key] = value;
+    },
+    t: function(key) {
+      return translations[key] || 'TRANSLATION NOT FOUND';
+    },
+    all: function() {
+      return translations;
+    }
+  };
+
+});