storage customization for react native

[ryanleecode]

Right now polyfire is using only local storage. This is a problem in react native since local storage doesn't exist and would be a problem in a web extension context as well. suggestion is to make the storage object generic and allow the user to pass in a storage object as a parameter.

[lowczarc]

You're right, it might be a better way of doing it.
I'm pretty sure this is not the only place where it depends on node/browser API though.

We should add tests for theses environment first or we will definitely break them accidentally at some point since we are developing mainly on node/browser.