started passing in the collection as the third argument to _.each iterators (Issue #1)

index.html

@@ -171,7 +171,9 @@
         <br />
         Iterates over a <b>list</b> of elements, yielding each in turn to an <b>iterator</b>
         function. The <b>iterator</b> is bound to the <b>context</b> object, if one is
-        passed. If <b>list</b> is a JavaScript object, a pair with <b>key</b>
+        passed. Each invocation of <b>iterator</b> is called with three arguments,
+        <i>element</i>, <i>index</i>, and the <b>list</b>. 
+        If <b>list</b> is a JavaScript object, a pair with <b>key</b>
         and <b>value</b> properties will be yielded. If the list has an <b>each</b> 
         method of its own, it will be used instead. Delegates to the native 
         <b>forEach</b> function if it exists.

test/collections.js

@@ -29,6 +29,10 @@ $(document).ready(function() {
     _.each(obj, function(pair){ answers.push(pair.key); });
     equals(answers.join(", "), 'one, two, three', 'iterating over objects works, and ignores the object prototype.');
     delete obj.constructor.prototype.four;
+    
+    answer = null;
+    _.each([1, 2, 3], function(num, index, arr){ if (_.include(arr, num)) answer = true; });
+    ok(answer, 'can reference the original collection from inside the iterator');
   });
   
   test('collections: map', function() {

underscore.js

@@ -38,16 +38,16 @@
       if (obj.forEach) {
         obj.forEach(iterator, context);
       } else if (obj.length) {
-        for (var i=0, l = obj.length; i<l; i++) iterator.call(context, obj[i], i);
+        for (var i=0, l = obj.length; i<l; i++) iterator.call(context, obj[i], i, obj);
       } else if (obj.each) {
-        obj.each(function(value) { iterator.call(context, value, index++); });
+        obj.each(function(value) { iterator.call(context, value, index++, obj); });
       } else {
         var i = 0;
         for (var key in obj) if (Object.prototype.hasOwnProperty.call(obj, key)) {
           var value = obj[key], pair = [key, value];
           pair.key = key;
           pair.value = value;
-          iterator.call(context, pair, i++);
+          iterator.call(context, pair, i++, obj);
         }
       }
     } catch(e) {