upgrade to webpack 4

package.json

@@ -43,11 +43,10 @@
   ],
   "dependencies": {
     "clipboard": "^1.7.1",
-    "vue": "^2.5.2"
+    "vue": "^2.6.9"
   },
   "devDependencies": {
     "autoprefixer": "^7.1.5",
-    "autoprefixer-loader": "^3.2.0",
     "babel-core": "^6.26.0",
     "babel-eslint": "^8.0.1",
     "babel-loader": "^7.1.2",
@@ -61,17 +60,20 @@
     "eslint": "^5.6.0",
     "eslint-plugin-vue": "^5.0.0-beta.3",
     "file-loader": "^1.1.5",
-    "html-webpack-plugin": "^2.30.1",
+    "html-webpack-plugin": "^3.2.0",
     "node-sass": "^4.5.3",
+    "postcss-loader": "^3.0.0",
     "sass-loader": "^6.0.6",
     "style-loader": "^0.19.0",
+    "uglifyjs-webpack-plugin": "^2.1.2",
     "url-loader": "^0.6.2",
-    "vue-loader": "^13.3.0",
-    "vue-style-loader": "^3.0.3",
-    "vue-template-compiler": "^2.5.2",
-    "webpack": "^3.8.1",
+    "vue-loader": "^15.7.0",
+    "vue-style-loader": "^4.1.2",
+    "vue-template-compiler": "^2.6.9",
+    "webpack": "^4.29.6",
     "webpack-bundle-analyzer": "^3.0.2",
-    "webpack-dev-server": "^2.9.2",
+    "webpack-cli": "^3.3.0",
+    "webpack-dev-server": "3.1.11",
     "webpack-merge": "^4.1.0"
   }
 }