Updated README build icon (branch=master)

Author: rijnb

README.md

@@ -1,7 +1,7 @@
 # Mapcode Library for Java
 
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+[![Build Status](https://img.shields.io/travis/mapcode-foundation/mapcode-java.svg?maxAge=3600&branch=master)](https://travis-ci.org/mapcode-foundation/mapcode-java)
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