Integrate with Travis CI

Signed-off-by: Eric Wang <[email protected]>

Author: skygragon

README.md

@@ -2,6 +2,7 @@
 
 [![npm version](https://img.shields.io/npm/v/leetcode-cli.svg?style=flat)](https://www.npmjs.com/package/leetcode-cli)
 [![license](https://img.shields.io/npm/l/leetcode-cli.svg?style=flat)](https://github.com/skygragon/leetcode-cli/blob/master/LICENSE)
+[![Build](https://img.shields.io/travis/skygragon/leetcode-cli.svg?style=flat)](https://travis-ci.org/skygragon/leetcode-cli)
 
 A cli tool to enjoy leetcode!