title: process.env.NODE_ENV variables into scss via webpack
body: <p>Is there a way to reference a process.env.NODE_ENV in a scss file by passing it to the sass-loader in web-pack. If so anyone know how to go about this ? </p>
  
  <p>Here is my webpack module lodaers array. </p>
  
  <pre><code>module: {
      loaders: [
        { test: /\.js?$/,
          loader: 'babel-loader',
          include: path.join(__dirname, '../app'),
          exclude: /node_modules/
        },
        { test: /\.scss?$/,
          loader: 'style-loader!css-loader!sass-loader',
          include: path.join(__dirname, '../app', 'styles')
        },
        {
          test: /\.(jpe?g|png|gif|svg)$/i,
          include : path.join(__dirname, '../app', 'images'),
          loader  : 'file-loader?limit=30000&amp;name=[name].[ext]'
        },
        {
          test: /\.(ttf|eot|svg|woff(2)?)(\?[a-z0-9]+)?$/,
          include : path.join(__dirname, '../app', 'fonts'),
          loader: 'file-loader?name=fonts/[name].[ext]'
        }
      ] 
  </code></pre>
  
  <p>I even tried </p>
  
  <pre><code>      { test: /\.scss?$/,
          loader: 'style-loader!css-loader!sass-loader',
          include: path.join(__dirname, '../app', 'styles'),
          options: {
            data: "$env: " + process.env.NODE_ENV + ";"
          }
        }
  </code></pre>
  
  <p>but the above broke the build. 
  I just want a way to access a url in my scss file depending on the environment. 
  It doesn't have to be via webpack any ideas would help without hard coding it. 
  for example: </p>
  
  <pre><code>  .contact-transparent{
      width: 100%;
      height: 100%;
      background: url(process.env.NODE_ENV+'/home-background.jpg') left center no-repeat;
    }
  </code></pre>