message: Add socks4/4a into README
diff: @@ -460,8 +460,9 @@ Example configuration:
  It supports the following features:
  -* [x] Socks5 CONNECT command
  -* [x] Socks5 UDP ASSOCIATE command (partial)
  +* [x] SOCKS5 CONNECT command
  +* [x] SOCKS5 UDP ASSOCIATE command (partial)
  +* [x] SOCKS4/4a CONNECT command
  * [x] Various crypto algorithms
  * [x] Load balancing (multiple servers) and server delay checking
  * [x] [SIP004](https://github.com/shadowsocks/shadowsocks-org/issues/30) AEAD ciphers
  