fix(Readme): use master svg in ci build result

Author: ShannonDing

README.md

@@ -1,6 +1,6 @@
 ## RocketMQ Client Python
 [![License](https://img.shields.io/badge/license-Apache%202-4EB1BA.svg)](https://www.apache.org/licenses/LICENSE-2.0.html)
-[![TravisCI](https://travis-ci.org/apache/rocketmq-client-python.svg)](https://travis-ci.org/apache/rocketmq-client-python)
+[![TravisCI](https://travis-ci.org/apache/rocketmq-client-python.svg?branch=master)](https://travis-ci.org/apache/rocketmq-client-python)
 * RocketMQ Python client is developed on top of [rocketmq-client-cpp](https://github.com/apache/rocketmq-client-cpp), which has been proven robust and widely adopted within Alibaba Group by many business units for more than three years.
 
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