Support rediss:// urls
Support rediss:// urls

rediss:// is a valid scheme based on IANA :
https://www.iana.org/assignments/uri-schemes/prov/rediss

We (Heroku) would like to move secure redis connections forward, but
have this chicken and egg problem with some drivers. Drivers for other
languages already support rediss://

gomodule/redigo,garyburd/redigo