Add build and coverage badege to README.md
-# Cadence
+# Cadence [![Build Status](https://travis-ci.org/uber/cadence.svg?branch=master)](https://travis-ci.org/uber/cadence) [![Coverage Status](https://coveralls.io/repos/github/uber/cadence/badge.svg?branch=master)](https://coveralls.io/github/uber/cadence?branch=master)
Cadence is a distributed, scalable, durable, and highly available orchestration engine we developed at Uber Engineering to execute asynchronous long-running business logic in a scalable and resilient way.
