Change nest.rollup to return entry.value.

Fixes #3.

src/nest.js

@@ -8,8 +8,8 @@ export default function() {
       nest;
 
   function apply(array, depth, createResult, setResult) {
-    if (depth >= keys.length) return rollup
-        ? rollup(array) : (sortValues
+    if (depth >= keys.length) return rollup != null
+        ? rollup(array) : (sortValues != null
         ? array.sort(sortValues)
         : array);
 
@@ -38,18 +38,11 @@ export default function() {
   }
 
   function entries(map, depth) {
-    if (depth >= keys.length) return map;
-
-    var array = [],
-        sortKey = sortKeys[depth++];
-
-    map.each(function(value, key) {
-      array.push({key: key, values: entries(value, depth)});
-    });
-
-    return sortKey
-        ? array.sort(function(a, b) { return sortKey(a.key, b.key); })
-        : array;
+    if (++depth > keys.length) return map;
+    var array, sortKey = sortKeys[depth - 1];
+    if (rollup != null && depth >= keys.length) array = map.entries();
+    else array = [], map.each(function(v, k) { array.push({key: k, values: entries(v, depth)}); });
+    return sortKey != null ? array.sort(function(a, b) { return sortKey(a.key, b.key); }) : array;
   }
 
   return nest = {

test/nest-test.js

@@ -98,7 +98,7 @@ tape("nest.key(key).rollup(rollup).entries(array) aggregates values per key usin
   var a = {foo: 1},
       b = {foo: 1},
       c = {foo: 2};
-  test.deepEqual(collection.nest().key(function(d) { return d.foo; }).rollup(function(values) { return values.length; }).entries([a, b, c]), [{key: "1", values: 2}, {key: "2", values: 1}]);
+  test.deepEqual(collection.nest().key(function(d) { return d.foo; }).rollup(function(values) { return values.length; }).entries([a, b, c]), [{key: "1", value: 2}, {key: "2", value: 1}]);
   test.end();
 });