Adds possibility of order to aggregate method (#114)

lib/AggregateFunctions.js

@@ -30,6 +30,10 @@ function AggregateFunctions(opts) {
 			group_by = Array.prototype.slice.apply(arguments);
 			return this;
 		},
+		order: function (property, order) {
+			opts.order = [ property, order ];
+			return this;
+		},
 		get: function (cb) {
 			if (typeof cb != "function") {
 				throw new Error("You must pass a callback to Model.aggregate().get()");
@@ -56,6 +60,10 @@ function AggregateFunctions(opts) {
 				query.groupBy.apply(query, group_by);
 			}
 
+			if (opts.order) {
+				query.order.apply(query, opts.order);
+			}
+
 			opts.driver.execQuery(query.build(), function (err, data) {
 				if (err) {
 					return cb(err);

test/integration/test-aggregate-groupby-orderby.js

@@ -0,0 +1,28 @@
+var common     = require('../common');
+var assert     = require('assert');
+
+common.createConnection(function (err, db) {
+	common.createModelTable('test_aggregate_groupby_orderby', db.driver.db, function () {
+		common.insertModelData('test_aggregate_groupby_orderby', db.driver.db, [
+			{ id : 2, name : 'test1' },
+			{ id : 3, name : 'test1' },
+			{ id : 4, name : 'test1' },
+			{ id : 5, name : 'test2' }
+		], function (err) {
+			if (err) throw err;
+
+			var TestModel = db.define('test_aggregate_groupby_orderby', common.getModelProperties());
+
+			TestModel.aggregate().avg('id').count().groupBy('name').order('name', 'Z').get(function (err, rows) {
+				assert.equal(err, null);
+				assert.equal(Array.isArray(rows), true);
+				assert.equal(rows.length, 2);
+				assert.equal(rows[0].avg_id, 5);
+				assert.equal(rows[0].count, 1);
+				assert.equal(rows[1].avg_id, 3);
+				assert.equal(rows[1].count, 3);
+				db.close();
+			});
+		});
+	});
+});