Remove CircleCI (#557)

Author: jimmyjames

.circleci/config.yml

@@ -5,7 +5,7 @@
 
 ![A Java client library for the Auth0 Authentication and Management APIs.](https://cdn.auth0.com/website/sdks/banners/auth0-java-banner.png)
 
-[![CircleCI](https://img.shields.io/circleci/project/github/auth0/auth0-java.svg?style=flat-square)](https://circleci.com/gh/auth0/auth0-java/tree/master)
+![Build Status](https://img.shields.io/github/checks-status/auth0/auth0-java/master)
 [![Coverage Status](https://codecov.io/gh/auth0/auth0-java/branch/master/graph/badge.svg?style=flat-square)](https://codecov.io/github/auth0/auth0-java)
 [![License](http://img.shields.io/:license-mit-blue.svg?style=flat)](https://doge.mit-license.org/)
 [![Maven Central](https://img.shields.io/maven-central/v/com.auth0/auth0.svg?style=flat-square)](https://search.maven.org/#search%7Cga%7C1%7Cg%3A%22com.auth0%22%20AND%20a%3A%22auth0%22)