function composeReducer(nextReducer, previousReducer) {
  // compose the reducers when both parameters are functions
  if(typeof(nextReducer) === 'function' && typeof(previousReducer) === 'function') {
    return (state, action) => previousReducer(nextReducer(state, action), action);
  }

  // return the nextReducer
  return nextReducer;
}
Creates a new reducer by taking the output of the first reducer as state to the second
@param {Object} currentReducer - reducerMethod (state, action) to that we want to run as the state parameter for second reducer
@param {Object} previousReducer - reducerMethod (state, action) to run second