Update README.md

Author: Pavel Petroshenko

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 # LIS3DH 3-Axis Accelerometer
 
+[![Build Status](https://api.travis-ci.org/electricimp/LIS3DH.svg?branch=master)](https://travis-ci.org/electricimp/LIS3DH)
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 The [LIS3DH](http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00274221.pdf) is a 3-Axis MEMS accelerometer. The LIS3DH application note can be found [here](http://www.st.com/web/en/resource/technical/document/application_note/CD00290365.pdf). This sensor has extensive functionality and this class has not yet implemented all of it.
 
 The LPS25H can interface over I²C or SPI. This class addresses only I²C for the time being.