add ci status

README_en.md

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 [![license](http://img.shields.io/badge/license-BSD-blue.svg)](https://github.com/Tencent/TencentOS-tiny/blob/master/LICENSE)
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-blue.svg)](https://github.com/Tencent/TencentOS-tiny/pulls)
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+[![Build status](https://travis-ci.org/Tencent/TencentOS-tiny.svg?branch=master)](https://travis-ci.org/Tencent/TencentOS-tiny)
 # Introduction to TencentOS Tiny
 
 [TencentOS tiny](https://cloud.tencent.com/product/tos-tiny) is a real-time operating system developed by Tencent for the Internet of Things. It features low power consumption, low resource consumption, modularity, security and reliability, and can effectively improve the development efficiency of IoT terminal products. TencentOS tiny provides a streamlined RTOS core that can be tailored and configurable for rapid migration to a wide range of mainstream MCUs (such as the full range of STM32) and module chips. Moreover, based on the RTOS kernel, it provides a wealth of IoT components, and internally integrates mainstream IoT protocol stacks (such as CoAP/MQTT/TLS/DTLS/LoRaWAN/NB-IoT, etc.), which can help IoT terminals and services to quickly access Tencent. Cloud Internet of Things platform.
@@ -34,8 +34,9 @@ TencentOS tiny main architecture diagram, from bottom to top, mainly includes:
 ## 2、TencentOS tiny优势
 
 ### (1).Small size
-Minimum kernel: RAM 0.6KB, ROM 1.8KB
-Typical LoraWAN and Sensor Applications: RAM 3.3KB, ROM 12KB
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+Minimum kernel: RAM 0.6KB, ROM 1.8KB  
+Typical LoraWAN and Sensor Applications: RAM 3.3KB, ROM 12KB 
 ### (2).Low power consumption
 Minimum sleep power consumption as low as 2 uA
 Support for peripheral power management framework