doc: IgnorePlugin => NormalModuleReplacementPlugin, fixed #1315

examples/docs/en-US/i18n.md

@@ -26,13 +26,13 @@ Vue.component(Button.name, Button)
 Vue.component(Select.name, Select)
 ```
 
-The Chinese language pack is imported by default, even if you're using another language. But with `IgnorePlugin` provided by webpack you can ignore it when building:
+The Chinese language pack is imported by default, even if you're using another language. But with `NormalModuleReplacementPlugin` provided by webpack you can replace default locale:
 
 webpack.config.js
 ```javascript
 {
   plugins: [
-    new webpack.IgnorePlugin(/element-ui\/lib\/locale\/lang\/zh-CN/)
+    new webpack.NormalModuleReplacementPlugin(/element-ui[\/\\]lib[\/\\]locale[\/\\]lang[\/\\]zh-CN/, 'element-ui/lib/locale/lang/en')
   ]
 }
 ```

examples/docs/zh-CN/i18n.md

@@ -38,13 +38,13 @@ Vue.component(Button.name, Button)
 Vue.component(Select.name, Select)
 ```
 
-如果使用其它语言，默认情况下中文语言包依旧是被引入的，可以使用 webpack 的 IgnorePlugin 忽略掉它以减少打包后的文件体积。
+如果使用其它语言，默认情况下中文语言包依旧是被引入的，可以使用 webpack 的 NormalModuleReplacementPlugin 替换默认语言包。
 
 **webpack.config.js**
 ```javascript
 {
   plugins: [
-    new webpack.IgnorePlugin(/element-ui\/lib\/locale\/lang\/zh-CN/)
+    new webpack.NormalModuleReplacementPlugin(/element-ui[\/\\]lib[\/\\]locale[\/\\]lang[\/\\]zh-CN/, 'element-ui/lib/locale/lang/en')
   ]
 }
 ```
@@ -64,5 +64,5 @@ Vue.component(Select.name, Select)
   <li>韩语（ko）</li>
   <li>日语（ja）</li>
 </ul>
- 
+
 如果你需要使用其他的语言，欢迎贡献 PR：只需在 [这里](https://github.com/ElemeFE/element/tree/master/src/locale/lang) 添加一个语言配置文件即可。