[exercises/implement_map_with_reduce] Highlight bonus points for implementing thisArg.

Also fixes solution function name.

Closes timoxley#96.

Author: timoxley

exercises/implement_map_with_reduce/problem.md

@@ -24,6 +24,10 @@ console.log(output) // => [2,4,6,8,10]
 * input: an arbitrary Array of any type.
 * operation: an arbitrary Function which can be applied to items in `input`.
 
+## Hints
+
+* No need to implement the optional `thisArg` argument of `Array.prototype.map`, bonus points if you do!
+
 ## Resources
 
 * https://en.wikipedia.org/wiki/Reduce_(higher-order_function)

exercises/implement_map_with_reduce/solution/solution.js

@@ -1,4 +1,4 @@
-module.exports = function map(arr, fn, thisArg) {
+module.exports = function arrayMap(arr, fn, thisArg) {
   return arr.reduce(function(acc, item, index, arr) {
     acc.push(fn.call(thisArg, item, index, arr))
     return acc