Add CI status badge

Author: Erik Rigtorp

README.md

@@ -2,6 +2,7 @@ Simple Binary Encoding (SBE)
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 [![Javadocs](http://www.javadoc.io/badge/uk.co.real-logic/sbe-tool.svg)](http://www.javadoc.io/doc/uk.co.real-logic/sbe-tool)
+[![Build Status](https://travis-ci.org/real-logic/simple-binary-encoding.svg?branch=master)](https://travis-ci.org/real-logic/simple-binary-encoding)
 
 [SBE](https://github.com/FIXTradingCommunity/fix-simple-binary-encoding) is an OSI layer 6 presentation for 
 encoding and decoding binary application messages for low-latency financial applications. This repository contains