Add travis badge

Author: luc-github

README.md

@@ -2,7 +2,7 @@
 
 [![Join the chat at https://gitter.im/luc-github/ESP8266](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/luc-github/ESP8266?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 FW for ESP8266 used with 3D printer
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+[![Build Status](https://travis-ci.org/luc-github/ESP8266.svg?branch=master)](https://travis-ci.org/luc-github/ESP8266)    
 ##Description      
 Thanks to @disneysw for bringing this module idea    
 Thanks to @lkarlslund for suggestion about independant reset using GPIO2