chore(deps): update dependency webpack to v3.8.1

Author: renovate[bot]

package-lock.json

@@ -100,7 +100,7 @@
     "url-loader": "0.6.2",
     "vue-loader": "13.3.0",
     "vue-template-compiler": "2.5.2",
-    "webpack": "3.7.1",
+    "webpack": "3.8.1",
     "webpack-dev-middleware": "1.12.0",
     "webpack-hot-middleware": "2.20.0"
   }