improve dev experience

[jedwards1211]

debugging issues with createReducer etc. can be tricky because it's not immediately obvious where the problematic reducer was created. I need to figure out the best way to ease debugging in this case. One idea is to store a stack trace when createReducer etc. is called (as long as process.env.NODE_ENV !== 'production', and if applying the reducer throws an error, include the creation stack trace in that error somehow.