added build status

README.md

@@ -1,4 +1,4 @@
-JMSSerializerBundle
+JMSSerializerBundle [![Build Status](https://secure.travis-ci.org/schmittjoh/JMSSerializerBundle.png?branch=master)](http://travis-ci.org/schmittjoh/JMSSerializerBundle)
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 Documentation: