Cannot write independent tests because of module cache

[timvahlbrock]

Currently there is no possibility to create independent store instances to use for unit testing, because the module cache is reusing the same instance. There has been a function clearProxyCache, which is no out of used (it still exists but is literally empty). Perhaps something similar or a function to force the recreation of a store might be helpful. To help other users with this it would probably be good to re-add the "How to test" section to the readme that had been there in times of the clearProxyCache function.

[timvahlbrock]

This fork actually repurposed the clearProxyCache function to clear all of the caches in this commit.