Update css-loader to the latest version 🚀 and use postcss-loader and cssnano to minimize CSS (#1464)

* chore(package): update css-loader to version 1.0.0

* Require minimum Node 6.9

* Use `postcss-loader` and `cssnano` to minimize CSS

* chore(package): update lockfile

* Remove unnecessary `ident` and function

* chore(package): update cssnano to version 4.0.1

check-node-version.js

@@ -7,8 +7,8 @@ v = v.map(function(s){
     return parseInt(s);
 });
 var a = v[0], b = v[1], c = v[2];
-if (a < 6 || (a == 6 && b < 5)) {
-    console.error("Node 6.5 or later required for development. " +
+if (a < 6 || (a == 6 && b < 9)) {
+    console.error("Node 6.9 or later required for development. " +
                   "Version " + process.version + " found");
     process.exit(1);
 } else {

package.json

@@ -27,7 +27,8 @@
     "babel-register": "^6.26.0",
     "benchmark": "^2.1.4",
     "check-dependencies": "^1.1.0",
-    "css-loader": "^0.28.11",
+    "css-loader": "^1.0.0",
+    "cssnano": "^4.0.1",
     "eslint": "^5.0.0",
     "eslint-plugin-flowtype": "^2.40.1",
     "file-loader": "^1.1.11",
@@ -43,6 +44,7 @@
     "mini-css-extract-plugin": "^0.4.0",
     "mkdirp": "^0.5.1",
     "pako": "1.0.6",
+    "postcss-loader": "^2.1.5",
     "query-string": "^6.1.0",
     "rimraf": "^2.6.2",
     "selenium-webdriver": "^3.6.0",

webpack.common.js

@@ -40,12 +40,15 @@ const targets /*: Array<Target> */ = [
  */
 function createConfig(target /*: Target */, dev /*: boolean */,
         minimize /*: boolean */) /*: Object */ {
-    const cssLoader = {
-        loader: 'css-loader',
-        options: {
-            minimize, // cssnano
-        },
-    };
+    const cssLoaders /*: Array<Object> */ = [{loader: 'css-loader'}];
+    if (minimize) {
+        cssLoaders[0].options = {importLoaders: 1};
+        cssLoaders.push({
+            loader: 'postcss-loader',
+            options: {plugins: [require('cssnano')()]},
+        });
+    }
+
     return {
         mode: dev ? 'development' : 'production',
         context: __dirname,
@@ -74,14 +77,14 @@ function createConfig(target /*: Target */, dev /*: boolean */,
                     test: /\.css$/,
                     use: [
                         dev ? 'style-loader' : MiniCssExtractPlugin.loader,
-                        cssLoader,
+                        ...cssLoaders,
                     ],
                 },
                 {
                     test: /\.less$/,
                     use: [
                         dev ? 'style-loader' : MiniCssExtractPlugin.loader,
-                        cssLoader,
+                        ...cssLoaders,
                         'less-loader',
                     ],
                 },