Bump to Mix v4

package.json

@@ -14,9 +14,12 @@
         "bootstrap": "^4.0.0",
         "cross-env": "^5.1",
         "jquery": "^3.2",
-        "laravel-mix": "^2.0",
+        "laravel-mix": "^4.0.7",
         "lodash": "^4.17.5",
         "popper.js": "^1.12",
+        "resolve-url-loader": "^2.3.1",
+        "sass": "^1.15.2",
+        "sass-loader": "^7.1.0",
         "vue": "^2.5.17"
     }
 }

resources/js/app.js

@@ -18,9 +18,9 @@ window.Vue = require('vue');
  */
 
 // const files = require.context('./', true, /\.vue$/i)
-// files.keys().map(key => Vue.component(key.split('/').pop().split('.')[0], files(key)))
+// files.keys().map(key => Vue.component(key.split('/').pop().split('.')[0], files(key).default))
 
-Vue.component('example-component', require('./components/ExampleComponent.vue'));
+Vue.component('example-component', require('./components/ExampleComponent.vue').default);
 
 /**
  * Next, we will create a fresh Vue application instance and attach it to