fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade: - https://snyk.io/vuln/npm:clean-css:20180306 Latest report for icebob/vue-express-mongo-boilerplate: https://snyk.io/test/github/icebob/vue-express-mongo-boilerplate

Author: snyk-bot

package.json

@@ -98,7 +98,7 @@
  "passport-localapikey-update": "0.5.0",
  "passport-twitter": "1.0.4",
  "pretty-bytes": "4.0.2",
- "pug": "2.0.0-beta6",
+ "pug": "2.0.0",
  "require-webpack-compat": "3.0.0",
  "serve-favicon": "2.4.5",
  "slug": "0.9.1",