function replaceReducers(defaultReducers) {
  const merged = Object.assign({}, defaultReducers, store.asyncReducers);
  const combined = combineReducers(merged);
  store.replaceReducer(combined);
}
Register async loaded reducers in store and replace
current state-reducer with the a new reducer

@export
@param {Object} store - the store object
@param {Object} asyncReducer - async reducer modules