Update README.md

Author: Igor Chepurnoy

README.md

@@ -5,6 +5,7 @@ Widget based on Ion.RangeSlider extension http://ionden.com/a/plugins/ion.rangeS
 [![Latest Stable Version](https://poser.pugx.org/yii2mod/yii2-ion-slider/v/stable)](https://packagist.org/packages/yii2mod/yii2-ion-slider) 
 [![Total Downloads](https://poser.pugx.org/yii2mod/yii2-ion-slider/downloads)](https://packagist.org/packages/yii2mod/yii2-ion-slider) 
 [![License](https://poser.pugx.org/yii2mod/yii2-ion-slider/license)](https://packagist.org/packages/yii2mod/yii2-ion-slider)
+[![Build Status](https://travis-ci.org/yii2mod/yii2-ion-slider.svg?branch=master)](https://travis-ci.org/yii2mod/yii2-ion-slider)
 
 Installation 
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