Per a conversation on twitter with @jezdez about this, here's a stab at some docs. I've tried to strike a balance: I want to tell people about this option, but not directly provide the code to avoid copy-paste without thinking.
* Add simple backend
* Add test case for simple backend
* Add tests for mget backend method
* Fix redis mock mget implementation
* Make sure memory backend is thread safe
* Add docs section for memory backend
* Add test usage examples to docs
* Update docs for memory backend in testing
* Share memory storage between threads
