fix(index): don't scope imported selector classes

[apexskier]

This is part of an overall resolution to css-modules/icss#12

I've got a PR coming to for https://github.com/webpack-contrib/css-loader that will enable this there as well. webpack-contrib/css-loader#562

[TrySound]

@apexskier Do you use low level API to process modules? We have postcss-icss-values for this. And this package has messages contracts with values.

[apexskier]

My full setup uses css-loader. Does postcss-icss-values replace selector information? In my tests it doesn't appear to, both when run before and after postcss-icss-selectors in the postcss pipeline.

With or without postcss-icss-values, I think this is valuable, as it provides deeper conformance to the base css-modules spec (as I interpreted it).