v4

[rt2zz]

• support immutable state ( 🎈 thanks @rufman )
• return Promises in default storage engines
• return Promise from purge methods

@rufman thanks for the great work on supporting immutable from #113 and I apologize for taking so long to get it merged in! since it requires a full 5 extra config options, I propose the following: Lets release a new module redux-persist-immutable which wraps redux-persist and proxies in the necessary config as well as well as the redux-persist-transform-immutable transform.

Towards this end, I renamed the config options from e.g. config.stateSetter to config._stateSetter, since the intended usage is via a proxy module (or a higher order module if you will).

Let me know your thoughts. I am still working on a few more tweaks and adding more tests in preparation for v4, I hope to cut a release this week.

cc/ @corbt @marvinhagemeister @rufman

[rt2zz]

Also this adds promise support for purge #119 and static purgeStoredState export #127

[rufman]

@rt2zz Yeah I think not exposing any of those options directly is a good idea. I'll look at starting an implementation of a "higher order library" this week.