fix npm run dev fail bug

Author: purestart

package.json

@@ -28,8 +28,7 @@
   },
   "dependencies": {
     "vue": "^2.5.2",
-    "vue-router": "^3.0.1",
-    "webpack-dev-server": ">=3.1.11"
+    "vue-router": "^3.0.1"
   },
   "devDependencies": {
     "autoprefixer": "^7.1.2",