Update .travis (#244)

Author: glmapper

.coveralls.yml

@@ -12,4 +12,4 @@ script:
 - sh ./check_format.sh
 
 after_success:
-- mvn clean test cobertura:cobertura org.eluder.coveralls:coveralls-maven-plugin:report
+  - bash <(curl -s https://codecov.io/bash)

.travis.yml

@@ -1,7 +1,7 @@
 ## SOFATracer
 
 [![Build Status](https://travis-ci.com/sofastack/sofa-tracer.svg?branch=master)](https://travis-ci.com/sofastack/sofa-tracer)
-[![Coverage Status](https://coveralls.io/repos/github/sofastack/sofa-tracer/badge.svg?branch=master)](https://coveralls.io/github/sofastack/sofa-tracer?branch=master)
+[![Coverage Status](https://codecov.io/gh/sofastack/sofa-tracer/branch/master/graph/badge.svg)](https://codecov.io/gh/sofastack/sofa-tracer/branch/master)
 ![license](https://img.shields.io/badge/license-Apache--2.0-green.svg)
 [![Maven](https://img.shields.io/github/release/sofastack/sofa-tracer.svg)](https://github.com/sofastack/sofa-tracer/releases)