Advertise TLS support in the README?

[aranhoide]

Apparently, Carmine has been supporting TLS for a while via (-> conn-opts :spec :ssl-fn). This is documented in the wcar docstring, and it's not qualified as experimental anywhere in the source code, so I suppose it's a supported feature. I have tested a custom ssl-fn (with client verification and pinned server cert) and it works well.

Adding a bullet point to the Features list advertising such support in the README would help users requiring this support, and perhaps increase Carmine adoption.

(I'm assuming that the "Pluggable compression and encryption support (v2+)" refers to encrypting/compressing data at rest in redis, not encrypting/compressing the transport. If I'm wrong about this, I still suggest adding an explicit reference to SSL/TLS).