Update webpack text plugin dependency

Author: theteejster

package-lock.json

@@ -34,7 +34,7 @@
     "babel-preset-es2015": "^6.24.1",
     "copy-webpack-plugin": "^4.5.1",
     "css-loader": "^0.28.11",
-    "extract-text-webpack-plugin": "^2.1.2",
+    "extract-text-webpack-plugin": "^3.0.2",
     "file-loader": "^1.1.11",
     "html-webpack-plugin": "^3.2.0",
     "istanbul-instrumenter-loader": "^3.0.1",

package.json

@@ -103,8 +103,8 @@ module.exports = function makeWebpackConfig() {
       // Use style-loader in development.
 
       loader: isTest ? 'null-loader' : ExtractTextPlugin.extract({
-        fallbackLoader: 'style-loader',
-        loader: [
+        fallback: 'style-loader',
+        use: [
           {loader: 'css-loader', query: {sourceMap: true}},
           {loader: 'postcss-loader'}
         ],