Allow autoprefixer's browser versions to be configured

assets/build/config.js

@@ -26,6 +26,7 @@ const config = mergeWithConcat({
     watcher: !!argv.watch,
   },
   watch: [],
+  browsers: [],
 }, userConfig);
 
 config.watch.push(`${path.basename(config.paths.assets)}/${config.copy}`);

assets/build/webpack.config.js

@@ -155,7 +155,7 @@ let webpackConfig = {
         output: { path: config.paths.dist },
         context: config.paths.assets,
         postcss: [
-          autoprefixer({ browsers: ['last 2 versions', 'android 4', 'opera 12'] }),
+          autoprefixer({ browsers: config.browsers }),
         ],
       },
     }),