refact(es6): use es6 syntax.

* fixed #10, But iojs-2 not support Object.assign, so use object-assign
  shim instead for now.
* use es6 syntax.
* use eslint to instead jshint.

test/other-locales/zh-CN.js

@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = {
-  Email: '邮箱1'
-}
+  Email: '邮箱1',
+};