Make postcss happier

It's still complaining about duplicate plugins, but it's a warning and not an error.

package.json

@@ -54,6 +54,7 @@
     "copy-webpack-plugin": "^4.0.1",
     "core-js": "^2.4.1",
     "css-loader": "^0.28.0",
+    "cssnano": "^3.10.0",
     "extract-text-webpack-plugin": "^2.1.0",
     "file-loader": "^0.11.1",
     "html-loader": "^0.4.5",
@@ -61,7 +62,10 @@
     "jquery": "^3.2.1",
     "json-loader": "^0.5.4",
     "node-sass": "^4.5.2",
+    "postcss-cssnext": "^2.11.0",
+    "postcss-import": "^10.0.0",
     "postcss-loader": "^2.0.5",
+    "postcss-scss": "^1.0.0",
     "raw-loader": "^0.5.1",
     "reflect-metadata": "^0.1.10",
     "rimraf": "^2.6.1",

postcss.config.js

@@ -0,0 +1,8 @@
+module.exports = {
+    parser: 'postcss-scss',
+    plugins: {
+        'postcss-import': {},
+        'postcss-cssnext': {browsers: ['last 2 version']},
+        'cssnano': {}
+    }
+};

webpack.config.js

@@ -97,12 +97,7 @@ module.exports = function () {
                 },
                 sassLoader: {
                     //includePaths: [path.resolve(__dirname, "node_modules/foundation-sites/scss")]
-                },
-                postcss: [
-                    autoprefixer({
-                        browsers: ['last 2 version']
-                    })
-                ]
+                }
             }
         }),
         new CommonsChunkPlugin({