docs: remove duplicate badge in readme

Author: nodkz

README.md

@@ -1,9 +1,8 @@
 # mongodb-memory-server
 
-[![travis build](https://img.shields.io/travis/nodkz/mongodb-memory-server.svg)](https://travis-ci.org/nodkz/mongodb-memory-server)
+[![Travis](https://img.shields.io/travis/nodkz/mongodb-memory-server.svg)](https://travis-ci.org/nodkz/mongodb-memory-server)
 [![NPM version](https://img.shields.io/npm/v/mongodb-memory-server.svg)](https://www.npmjs.com/package/mongodb-memory-server)
 [![Downloads stat](https://img.shields.io/npm/dt/mongodb-memory-server.svg)](http://www.npmtrends.com/mongodb-memory-server)
-[![Travis](https://img.shields.io/travis/nodkz/mongodb-memory-server.svg?maxAge=2592000)](https://travis-ci.org/nodkz/mongodb-memory-server)
 [![Commitizen friendly](https://img.shields.io/badge/commitizen-friendly-brightgreen.svg)](http://commitizen.github.io/cz-cli/)
 ![TypeScript compatible](https://img.shields.io/badge/typescript-compatible-brightgreen.svg)