[dev]修改package.json的配置，升extract-text-webpack-plugin的版本号到2.1.2，解决编译中由于extract-text-webpack-plugin中query方法调用出现的问题

[leewind]

Please makes sure these boxes are checked before submitting your PR, thank you!

• [ ] Make sure you follow the contributing guide.
• [ ] Rebase before creating a PR to keep commit history clear.
• [ ] Add some descriptions and refer relative issues for you PR.