importation of style files from modules that I depend on.

I am trying to use react-toolbox which provides widgets and comes with its own style sheets.
http://react-toolbox.com/
but whenever I try to import any element, I get this error:

`
[0] ==> 🚧 Webpack development server listening on port 3001
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/animations/slide-left.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/animations/slide-right.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/animations/zoom-in.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/animations/zoom-out.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/ripple/style.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/button/style.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/date_picker/style.calendar.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/overlay/style.scss
[1] [webpack-isomorphic-tools] [error] asset not found: ./~/react-toolbox/lib/dialog/style.scss
`

This happens with other libraries also. I am also tried to use react-bootstrap-datetimepickered
According to here, https://github.com/quri/react-bootstrap-datetimepicker/issues/141
I suppose to include the css file this way:

`
import 'react-bootstrap-datetimepicker/css/bootstrap-datetimepicker.min.css';
`
but I keep getting this error:
`[require-hook] Trying to load "bootstrap-datetimepicker.min.css" as a "*.js"`

I even changed webpack for dev.config.js to include .css files:

`
{
test: /.css$/, // Only .css files
loader: 'style!css' // Run both loaders
},

`

Does anyone have trouble loading CSS or SCSS style files that are used in different libraries installed via NPM?