docs: is "Always pass the store to selectors" still true?

[davidgilbertson]

https://github.com/davidgilbertson/react-recollect#always-pass-the-store-to-selectors

I think this might not be an issue any more. Write some tests and update.

While I'm at it, check if it works fine with third party Context (e.g. material-ui theme). Write some tests and update https://github.com/davidgilbertson/react-recollect#can-i-use-this-with-context

Resolved by #75