Fix step3 in `transducing in javascript` from `getify`

step3.js

function add1(v) { return v + 1; }
function isOdd(v) { return v % 2 == 1; }
function sum(total,v) { return total + v; }

function listReduction(list,v) {
	list.push(v);
	return list;
}

function mapReducer(fn) {
	return function(reductionFn){
		return function(list,v){
			return reductionFn( list, fn(v) );
		};
	};
}

function filterReducer(fn) {
	return function(reductionFn){
		return function(list,v){
			if (fn(v)) return reductionFn( list, v );
			return list;
		};
	};
}

// No need to use this function
function listSumReduction(list,v) {
	list[0] = sum(list[0] || 0,v);
	return list;
}

function identity(v) { return v; }

function reduceReducer(reductionFn){
	return mapReducer(identity)(reductionFn);
}


var list = [2,5,8,11,14,17,20];

list
.reduce( mapReducer(add1)(listReduction), [] )
.reduce( filterReducer(isOdd)(listReduction), [] )
.reduce( reduceReducer(sum));

And since map(identity) == identity

reduceReducer(sum) ==
mapReducer(identity)(sum) ==
id(sum) ==
sum