Update to Webpack 4

[kaihendry]

https://github.com/vuejs-templates/webpack-simple/blob/master/template/package.json

[robcresswell]

See #182

[borodadada]

need official update! with options - without ssas

[JoseGoncalves]

I've added Webpack v4 support to this template, please check my GithHub repo.

If you want to test it, execute, with vue-cli 2.x:

vue init JoseGoncalves/webpack-simple my-project

Feedback is appreciated. BTW, I never tested the sass stuff.

[bi-kai]

hope upgrade webpack to 4.x officially.