Support Redux 4

[nickserv]

Redux 4 is out. The tests already pass using it, but redux-devtools-extension needs to update its peer dependency (blocked by zalmoxisus/redux-devtools-extension#490). I'd like wait until this is fixed before adjusting our peer dependencies to reduce confusion and limit peer dependencies seen by users, this issue is just here to remind us to adjust the peer dependency after redux-devtools-extension updates.

[nickserv]

@markerikson The devtools extension was updated for Chrome and npm, but not Firefox. Do we want to continue waiting?

[tayler-king]

I personally think it should be updated to support Redux 4. Been quite a while, and now that the Chrome extension has been updated the Firefox extension should be published soon.

[nickserv]

True, we've waited long enough, and most devs are on Chrome anyway. Firefox users can always stay on older Redux versions, install the new extension from source, or instantiate the devtools manually.