Add coverage to README

Signed-off-by: Isaac Hier <isaachier@gmail.com>

Author: isaachier

README.md

@@ -1,2 +1,11 @@
+[![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov] [![OpenTracing 1.0 Enabled][ot-img]][ot-url]
+
 # cpp-client
 C++ OpenTracing binding for Jaeger
+
+[ci-img]: https://travis-ci.org/jaegertracing/cpp-client.svg?branch=master
+[ci]: https://travis-ci.org/jaegertracing/cpp-client
+[cov-img]: https://codecov.io/gh/jaegertracing/cpp-client/branch/master/graph/badge.svg
+[cov]: https://codecov.io/gh/jaegertracing/cpp-client
+[ot-img]: https://img.shields.io/badge/OpenTracing--1.0-enabled-blue.svg
+[ot-url]: http://opentracing.io