Seeed:Arduino: Add travis build status

README.md

@@ -1,4 +1,4 @@
-Grove_barometer HP20x
+Grove_barometer HP20x  [![Build Status](https://travis-ci.com/Seeed-Studio/Grove_Barometer_HP20x.svg?branch=master)](https://travis-ci.com/Seeed-Studio/Grove_Barometer_HP20x)
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 ![](https://raw.githubusercontent.com/SeeedDocument/Grove-Barometer-High-Accuracy/master/img/Grove-Barometer-High-Accuracy.jpg)