Add codecov coverage badge
# AssertJ - Fluent assertions for java
-`master:` [![Build Status (master)](https://travis-ci.org/joel-costigliola/assertj-core.svg?branch=master)](https://travis-ci.org/joel-costigliola/assertj-core) `2.x:` [![Build Status (2.x)](https://travis-ci.org/joel-costigliola/assertj-core.svg?branch=2.x)](https://travis-ci.org/joel-costigliola/assertj-core/branches) [![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.assertj/assertj-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.assertj/assertj-core)
+`master:` [![Build Status (master)](https://travis-ci.org/joel-costigliola/assertj-core.svg?branch=master)](https://travis-ci.org/joel-costigliola/assertj-core)
+`2.x:` [![Build Status (2.x)](https://travis-ci.org/joel-costigliola/assertj-core.svg?branch=2.x)](https://travis-ci.org/joel-costigliola/assertj-core/branches)
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.assertj/assertj-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.assertj/assertj-core)
+[![Coverage Status](https://codecov.io/github/joel-costigliola/assertj-core/coverage.png?branch=master)](https://codecov.io/github/joel-costigliola/assertj-core?branch=master)
AssertJ provides a rich and intuitive set of strongly-typed assertions to use for unit testing (either with JUnit or TestNG).
