Codecov badge added

README.md

@@ -2,6 +2,7 @@
 
 [![Build Status](https://travis-ci.org/supanadit/jwt-go.svg?branch=master)](https://travis-ci.org/supanadit/jwt-go)
 [![Go Report Card](https://goreportcard.com/badge/github.com/supanadit/jwt-go)](https://goreportcard.com/report/github.com/supanadit/jwt-go)
+[![codecov](https://codecov.io/gh/supanadit/jwt-go/branch/master/graph/badge.svg)](https://codecov.io/gh/supanadit/jwt-go)
 
 A JWT library for Golang and easy to use, but this is not original library meaning this library depends on other library such as [jwt-go](https://github.com/dgrijalva/jwt-go) which is the original JWT library for golang, also [mapstructure](github.com/mitchellh/mapstructure), and [bcrypt](golang.org/x/crypto/bcrypt).