[bug]: webpack fails to build in production

[ali-garajian]

Hi there!
According to this OccurrenceOrderPlugin is now enabled by default, and there's no need to include it as a plugin anymore;
So, you can just change this line
plugins: [new CleanWebpackPlugin(), new webpack.optimize.OccurrenceOrderPlugin()]
to this
plugins: [new CleanWebpackPlugin()]
in webpack.production.js, and the error goes away.

BTW, thanks for this setup. I'm fairly new to node, and this repo answered a lot of questions for me :)

[JaylanChen]

Sorry, I may not have noticed the notice of GitHub, so I didn't see this issue until now .

Thanks for your reminding, I will fix this bug immediately.