add debian sid instructions

README.md

@@ -26,6 +26,9 @@ remote server.
     apt-get install python-pip python-m2crypto
     pip install shadowsocks
 
+Or simply `apt-get install shadowsocks` if you have [Debian sid] in your
+source list.
+
 #### CentOS:
 
     yum install m2crypto python-setuptools
@@ -117,6 +120,7 @@ Bugs and Issues
 [Build Status]:      https://img.shields.io/travis/clowwindy/shadowsocks/master.svg?style=flat
 [Chinese Readme]:    https://github.com/clowwindy/shadowsocks/wiki/Shadowsocks-%E4%BD%BF%E7%94%A8%E8%AF%B4%E6%98%8E
 [Chrome Standalone]: https://support.google.com/installer/answer/126299
+[Debian sid]:        https://packages.debian.org/unstable/python/shadowsocks
 [iOS]:               https://github.com/shadowsocks/shadowsocks-iOS/wiki/Help
 [Issue Tracker]:     https://github.com/clowwindy/shadowsocks/issues?state=open
 [Mailing list]:      http://groups.google.com/group/shadowsocks