Replace `sanity` language in combineReducers (#2335)
Replace `sanity` language in combineReducers (#2335)

This replaces `sanityError` and `assertReducerSanity` with more descriptive, more inclusive language that describes what the check is actually doing (checking and asserting the shape).
gaearon/redux,CompuIves/redux,lifeiscontent/redux,CompuIves/redux,gaearon/redux,roth1002/redux,roth1002/redux,lifeiscontent/redux