Added Travis and Coveralls badges. (#135)

Author: jkohen

README.md

@@ -3,6 +3,9 @@
 This repository contains a sidecar for the Prometheus server that can send
 metrics to Stackdriver. This is based on [this design](docs/design.md).
 
+[![Build Status](https://travis-ci.com/Stackdriver/stackdriver-prometheus-sidecar.svg?branch=master)](https://travis-ci.com/Stackdriver/stackdriver-prometheus-sidecar)
+[![Coverage Status](https://coveralls.io/repos/github/Stackdriver/stackdriver-prometheus-sidecar/badge.svg?branch=master)](https://coveralls.io/github/Stackdriver/stackdriver-prometheus-sidecar?branch=master)
+
 ## Installation
 
 To install the sidecar on a local machine run: