update webpack-dev-server to address CVE-2018-14732

  * https://cve.circl.lu/cve/CVE-2018-14732
  * webpack/webpack-dev-server#1445

Author: alexdean

package.json

@@ -27,6 +27,6 @@
     "eslint": "^5.5.0",
     "eslint-plugin-react": "^7.11.1",
     "plop": "^2.1.0",
-    "webpack-dev-server": "2.11.2"
+    "webpack-dev-server": "3.7.2"
   }
 }