webpack mode should be 'none' unless embark's mode is 'production'

lib/pipeline/webpackProcess.js

@@ -38,7 +38,7 @@ class WebpackProcess extends ProcessWrapper {
   webpackRun(filename, options, includeModules, importsList, detectErrors, realCwd, callback) {
     const self = this;
     let defaultOptions = {
-      mode: self.env === 'development' ? 'none' : 'production',
+      mode: self.env === 'production' ? 'production' : 'none',
       // devtool: self.env === 'development' ? 'source-map' : false,
       // pipeline would need to copy .map files to dist/ target dir
       // note: generating full source maps ('source-map') roughly doubles build time