sass @import directives is ignored

Hi again.

We widely using '@import' directive in our project and it seems to be not supported for now in babel-plugin-react-css-modules. I also dig sources and found nothing in postcss pipeline that could process it.

**Would do you like to integrate postcss plugin for @import handling?**

A likely candidate is postcss-import plugin. It has one problem: it is asynchronous. So it break your flow, because of `lazyResult.root` usage. It is only works with syncronous plugins (I also unearth that this is not recommended approach: http://api.postcss.org/LazyResult.html#root).

Sync mode will not be implemented according to postcss/postcss-import#180 and postcss/postcss-import#293 but there is two workarounds:

1. Use postcss-import 7.x.x which is syncronous. I try and it works fine for a quick look.
2. Take a look at https://github.com/css-modules/postcss-icss-import which is reffered in postcss/postcss-import#293. But as author said it is in beta now and not yet working.

What do you think about?

Commencez par le pipeline PostCSS et son utilisation de lazyResult.root, puis examinez les options de postcss-import et postcss-icss-import mentionnées dans l’issue. Comparez les contraintes synchrones et asynchrones, et prenez en compte les solutions de contournement documentées. Le travail est terminé lorsque les directives Sass @import sont traitées sans perturber le flux existant du plugin.

Rédigé par le modèle d'indexation à partir du texte de l'issue.