Add a note for url(...) with css-modules in webpack.

[boopathi]

When you use cssnext with webpack's css-loader in module mode, url(./file) is transformed to url(file). This is done by postcss-url included in cssnext. Because of this issue, if you use url(./image.png), the css-loader?module gets it as url(image.png) and treats it as a module and searches in moduleDirectories rather than the relative path.

So, with css-loader module mode, I guess it is correct to use { url: false } option in cssnext which is propagated to postcss-url. So can we add a note about this in this repo?

Related issues and discussions:

• realtive paths for url(...) in css fails flipkart-incubator/phrontend-webpack#8
• https://gitter.im/postcss/postcss?at=55d5cd8280eb5af935921b1c
• boopathi/css-loader-test-2@835eb41

[MoOx]

I think we should fix the issue in postcss-url, which should not change path like that.

[MoOx]

postcss-cssnext do not handle url anymore (cssnext is now postcss-cssnext. cssnext is deprecated.) See postcss-cssnext migration guide http://cssnext.io/postcss/