Add skype for English user.

 # Simple-RTMP-Server
 
 [![CircleCI](https://circleci.com/gh/ossrs/srs/tree/2.0release.svg?style=svg)](https://circleci.com/gh/ossrs/srs/tree/2.0release)
-[![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/ossrs/srs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 [![Wechat](https://cloud.githubusercontent.com/assets/2777660/22814959/c51cbe72-ef92-11e6-81cc-32b657b285d5.png)](https://github.com/ossrs/srs/wiki/v1_CN_Contact#wechat)
 [<img width="52" alt="Skype" src="https://cloud.githubusercontent.com/assets/2777660/24329166/3821a328-1230-11e7-844a-506a5d17dd3d.png">](https://github.com/ossrs/srs/wiki/v1_EN_Contact#skype-or-gitter)