v2.6.0

Add experimental HTTP/TLS obfuscating as an optional extension of shadowsocks protocol.

More discussions can be found here: shadowsocks/shadowsocks-org#26

As this feature is still a SIP (Shadowsocks Improvement Proposal), it's very unstable and experimental. So,

1. Don't enable it unless you know what it is.
2. Be very careful when using it in production environment.