Allow using multiple storages

[tinbka]

Implement https://github.com/seamusabshere/cache_method/issues/2 The implementation was a test task from a scammer client on Upwork. Look for another "test puzzle", Alex.

Yes, I know this project is dead, lol.

[wbeckler]

I am the Upwork client who was using this issue as a test task. I like to use puzzles before high-stakes hires, and this puzzle has the added benefit of improving a library. I'm sorry if it appeared as a scam, but that is not the intention. We are growing our team of Ruby developers and we had hoped to use this puzzle before a PR was actually submitted. Unfortunately, we will have to find a new puzzle because a solution is now out there, although, it's not exactly a winning solution.