chore(readme): remove Greenkeeper badge (#101)

Co-authored-by: greenkeeper[bot] <23040076+greenkeeper[bot]@users.noreply.github.com>

README.md

@@ -4,7 +4,7 @@
 [![Build Status](https://travis-ci.org/markis/jest-ratchet.svg?branch=master)](https://travis-ci.org/markis/jest-ratchet)
 [![Coverage Status](https://coveralls.io/repos/github/markis/jest-ratchet/badge.svg?branch=master)](https://coveralls.io/github/markis/jest-ratchet?branch=master)
 [![Known Vulnerabilities](https://snyk.io/test/github/markis/jest-ratchet/badge.svg?targetFile=package.json)](https://snyk.io/test/github/markis/jest-ratchet?targetFile=package.json)
-[![Greenkeeper badge](https://badges.greenkeeper.io/markis/jest-ratchet.svg)](https://greenkeeper.io/)
+
 
 Ratchet up code coverage - keep test coverage going only one direction -- up