fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-SHAJS-12089400

Author: snyk-bot

package.json

@@ -53,7 +53,7 @@
     "semver": "^5.3.0",
     "style-loader": "0.13.1",
     "url-loader": "0.5.7",
-    "webpack": "1.13.1",
+    "webpack": "2.2.0",
     "webpack-dev-server": "1.14.1"
   },
   "devDependencies": {