add command to run postcss cssnext

[fraserxu]

This pull request use css-next to build css into app/assets/stylesheets/guide/application.css

• To build production css npm run build-css
• To auto compile css for dev npm run watch-css

Here's a list of plugin I have:

{
  "use": [
    "postcss-import",
    "postcss-url",
    "postcss-cssnext",
    "postcss-browser-reporter",
    "postcss-reporter"
  ]
}

Note that autoprefixer and cssnano(compressor) are part of postcss-cssnext so no need to include it here.

To start all the front-end build task, just run npm run watch, and npm run build to build all the assets for production.

[jordanlewiz]

👍 great stuff!! Could you also please add some detailed instructions to the wiki https://github.com/envato/guide/wiki/Developing thanks

[fraserxu]

Sure thing @jordanlewiz I'll add more documentation when the setup is done. Meanwhile, does @thefoxis has access to this repo? :D