docs(readme): Add badge for known vulnerabilities

Author: dalelotts

README.md

@@ -11,6 +11,7 @@ Native AngularJS datetime picker directive styled by Twitter Bootstrap 3
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 [![JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg)](http://standardjs.com/)
 [![Commitizen friendly](https://img.shields.io/badge/commitizen-friendly-brightgreen.svg)](http://commitizen.github.io/cz-cli/)
+[![Known Vulnerabilities](https://snyk.io/test/npm/angular-bootstrap-datetimepicker/badge.svg)](https://snyk.io/test/npm/angular-bootstrap-datetimepicker)
 [![PayPal donate button](http://img.shields.io/paypal/donate.png?color=yellow)](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=F3FX5W6S2U4BW&lc=US&item_name=Dale%20Lotts&item_number=angular%2dbootstrap%2ddatetimepicker&currency_code=USD&bn=PP%2dDonationsBF%3abtn_donate_SM%2egif%3aNonHosted "Donate one-time to this project using Paypal")
 <a href="https://twitter.com/intent/tweet?original_referer=https%3A%2F%2Fabout.twitter.com%2Fresources%2Fbuttons&amp;text=Check%20out%20this%20%23AngularJS%20directive%20that%20makes%20it%20dead%20simple%20for%20users%20to%20select%20dates%20%26%20times&amp;tw_p=tweetbutton&amp;url=https%3A%2F%2Fgithub.com%2Fdalelotts%2Fangular-bootstrap-datetimepicker&amp;via=dalelotts" target="_blank">
   <img src="http://jpillora.com/github-twitter-button/img/tweet.png"></img>