title: Webpack CSS loader won't parse comments
body: <p>I'm using react starter kit and I'm trying to import the SCSS files from bootstrap (installed via NPM) and it's complaining about the comments:</p>
  
  <pre><code>    ERROR in ./~/css-loader?sourceMap&amp;modules&amp;localIdentName=[name]_[local]_[hash:base64:3]!./~/postcss-loader!./~/bootstrap-sass/assets/stylesheets/_bootstrap.scss
  /Users/jamessherry/sites/business_website/node_modules/bootstrap-sass/assets/stylesheets/_bootstrap.scss:7:1: Unknown word
  
  // Core variables and mixins
  ^
  @import "bootstrap/variables";
  
  ERROR in ./~/css-loader?sourceMap&amp;modules&amp;localIdentName=[name]_[local]_[hash:base64:3]!./~/postcss-loader!./~/bootstrap-sass/assets/stylesheets/_bootstrap.scss
  Module build failed: TypeError: Cannot read property 'toString' of undefined
      at new Input (/Users/jamessherry/sites/business_website/node_modules/postcss/lib/input.js:31:23)
      at parse (/Users/jamessherry/sites/business_website/node_modules/postcss/lib/parse.js:22:17)
      at new LazyResult (/Users/jamessherry/sites/business_website/node_modules/postcss/lib/lazy-result.js:61:24)
      at Processor.process (/Users/jamessherry/sites/business_website/node_modules/postcss/lib/processor.js:34:16)
      at processCss (/Users/jamessherry/sites/business_website/node_modules/css-loader/lib/processCss.js:188:11)
      at Object.module.exports (/Users/jamessherry/sites/business_website/node_modules/css-loader/lib/loader.js:24:2)
   @ ./~/bootstrap-sass/assets/stylesheets/_bootstrap.scss 2:18-178 18:6-24:8 19:25-185
  </code></pre>
  
  <p>Here's the import in app.js</p>
  
  <pre><code>import emptyFunction from 'fbjs/lib/emptyFunction';
  import './../../../node_modules/bootstrap-sass/assets/stylesheets/_bootstrap.scss';
  import s from './App.scss';
  </code></pre>
  
  <p>Then put it through the webpack loaders:</p>
  
  <pre><code>, {
      test: /\.scss$/,
      loaders: [
        'isomorphic-style-loader',
        'css-loader?' + (DEBUG ? 'sourceMap&amp;' : 'minimize&amp;') +
        'modules&amp;localIdentName=[name]_[local]_[hash:base64:3]',
        'postcss-loader',
      ],
    }
  </code></pre>
  
  <p>Does anybody have any ideas why?</p>
  
  <p>Thanks</p>
  
  <p>James</p>