added snyk vulerabilities badge

README.md

@@ -2,8 +2,10 @@
 
 [![Build Status](https://secure.travis-ci.org/node-nock/nock.svg?branch=master)](http://travis-ci.org/node-nock/nock?branch=master)
 [![Coverage Status](https://coveralls.io/repos/github/node-nock/nock/badge.svg?branch=master)](https://coveralls.io/github/node-nock/nock?branch=master)
+[![Known Vulnerabilities](https://snyk.io/test/npm/nock/badge.svg)](https://snyk.io/test/npm/nock)
 [![Chat](https://img.shields.io/badge/help-gitter-eb9348.svg?style=flat)](https://gitter.im/node-nock/nock)
 
+
 Nock is an HTTP mocking and expectations library for Node.js
 
 Nock can be used to test modules that perform HTTP requests in isolation.