message: refactor sourceMapFilename to use file
  It's correcting to use [file] instead [name] in order to support work together with ExtractTextPlugin souremaps
  Inspired by:
diff: @@ -71,7 +71,7 @@ module.exports = function (options) {
  *
  * See: http://webpack.github.io/docs/configuration.html#output-sourcemapfilename
  */
  - sourceMapFilename: '[name].map',
  + sourceMapFilename: '[file].map',
  /** The filename of non-entry chunks as relative path
  * inside the output.path directory.
  