Add experimental HTTP/TLS obfuscating as an **optional extension** of shadowsocks protocol.
More discussions can be found here: https://github.com/shadowsocks/shadowsocks-org/issues/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.
Tests show that EL6 is too old to support `%elif` statement (which is very stupid).
And revert dependency `openssl-libs` to `openssl` because of
inconsistent names in EL6.
1. Remove function `get_att_val`:
That function uses `eval` to set default values for bash variables.
Because it is very dangerous to use `eval` (someone call it the plague of shell scripting), I'd like to use the bash builtin to do that.
2. Double quote all variables to avoid unexpected expansion when using it.
it's not conflicted with shadowsocks-python now. users can install both python and libev
ports of shaowsocks now. but they should migrate their old configuration file from
/etc/shadowsocks/config.json to /etc/shadowsocks-libev/config.json