add travisci badge
<img align="right" width="100" height="100" src="https://raw.githubusercontent.com/laixintao/iredis/master/docs/assets/logo.png" />
[![CircleCI](https://circleci.com/gh/laixintao/iredis.svg?style=svg)](https://circleci.com/gh/laixintao/iredis)
+[![TravisCI](https://travis-ci.org/laixintao/iredis.svg?branch=master)](https://travis-ci.org/laixintao/iredis)
[![PyPI version](https://badge.fury.io/py/iredis.svg)](https://badge.fury.io/py/iredis)
![Python version](https://badgen.net/badge/python/3.6%20|%203.7%20|%203.8/)
[![Chat on telegram](https://badgen.net/badge/icon/join?icon=telegram&label=usergroup)](https://t.me/iredis_users)
