Add Redis support

[softinio]

Add Redis support as an alternative to sqlite

This would be a great feature as it will make this solution easier to use in an enterprise production environment as getting a redis instance shared amonst multiple instances of your app is very easy and cost effective to use.

[Jonatha-Varjao]

This is trully a neat idead, I stumped in this repository by acident, stayed by the elegant problem solved approuch. I'm diving into the code base and maybe in a couple of days a can bring an PR.

[karlicoss]

Gave it an initial try (in an isolated test), seems like writing to redis cache might be a bit slow, but reading can be much faster than sqlite!
Supporting in cachew will require a bit of refactoring, especially to support sqlite at the same time, but looks promising so I might try it soon

[karlicoss]

had another go at redis, overall don't think it's worth it, writing is much much slower https://github.com/karlicoss/cachew/tree/redis