Expand Padrino::Cache to support all features of underlying cache

I'm specifically referring to Redis, but I imagine other backends have cool feature sets as well.

Anyways, I was thinking it would be nice if I could specify some sort of flag which made the API for caching more specific depending on which caching backend you were using. 

I'm kicking around a few code ideas that might work, but it's also possible that you don't want this functionality.
