title: sass-loader with extract-text-plugin not outputting file
body: <p>I have configured my <code>webpack.config.js</code> as following:</p>
  
  <pre><code>var debug = process.env.NODE_ENV !== "production";
  var webpack = require('webpack');
  var path = require('path');
  
  // plugins
  var ExtractTextPlugin = require('extract-text-webpack-plugin');
  
  module.exports = {
    context: path.join(__dirname, "src"),
    devtool: debug ? "inline-sourcemap" : null,
    entry: "./js/init.js",
    module: {
      loaders: [
        {
          test: /\.jsx?$/,
          exclude: /(node_modules|bower_components)/,
          loader: 'babel',
          query: {
            presets: ['react', 'es2015', 'stage-0'],
            plugins: ['react-html-attrs', 'transform-decorators-legacy', 'transform-class-properties',],
          }
        },
        {
          test: /\.json$/,
          include: /node_modules/,
          loader: 'json-loader'
        },
        {
          test: /\.scss$/,
          loaders: ExtractTextPlugin.extract(
            'style',
            'css!sass'
          )
        }
      ]
    },
    output: {
      path: __dirname + "/src/",
      filename: "app.js"
    },
    plugins: debug ? [] : [
      new webpack.optimize.DedupePlugin(),
      new webpack.optimize.OccurenceOrderPlugin(),
      new webpack.optimize.UglifyJsPlugin({ mangle: false, sourcemap: false }),
      new ExtractTextPlugin('default.css'),
    ],
    devServer: {
      port: 3000,
      historyApiFallback: {
        index: 'index.html'
      }
    },
    sassLoader: {
      includePaths: [path.resolve(__dirname, "src/css/sass")]
    },
    resolve: {
      alias: {
        '#': path.resolve(__dirname, 'src/js'),
        '!': path.resolve(__dirname, 'src/css/sass')
      }
    },
  };
  </code></pre>
  
  <p>And this is my file structure:</p>
  
  <pre><code>- src
  -- css
  --- sass
  ---- default.scss
  -- js
  -- index.html
  </code></pre>
  
  <p>Yet I don't see my <code>default.css</code> file exported anywhere when I run <code>webpack dev server</code>. Does it not work with <code>webpack dev server</code>?</p>
  
  <p>Edit: Simply running <code>webpack</code> does not work either.</p>