Ensure done iterations are sorted numerically.

Chrome sorts object keys numerically by default, so this hadn't
been showing up in my dev environment.

This guarantees the done iterations will be in the
correct numeric order when rebuilding the project iterations.

Fixes fulcrum-agile#57

public/javascripts/models/iteration.js

@@ -113,7 +113,7 @@ var Iteration = Backbone.Model.extend({
     var end = parseInt(endIteration.get('number'), 10);
 
     if (end < start) {
-      throw "end iteration number must be greater than start iteration number";
+      throw "end iteration number:" + end + " must be greater than start iteration number:" + start ;
     }
 
     var missing_range = _.range(start, end);

public/javascripts/models/project.js

@@ -202,13 +202,18 @@ var Project = Backbone.Model.extend({
     // Clear the project iterations
     this.iterations = [];
 
-    var done_iterations = _.groupBy(this.stories.column('#done'),
+    var doneIterations = _.groupBy(this.stories.column('#done'),
                                     function(story) {
                                       return story.iterationNumber();
                                     });
 
-    _.each(done_iterations, function(stories, iterationNumber) {
+    // groupBy() returns an object with keys of the iteration number
+    // and values of the stories array.  Ensure the keys are sorted
+    // in numeric order.
+    var doneNumbers = _.keys(doneIterations).sort();
 
+    _.each(doneNumbers, function(iterationNumber) {
+      var stories = doneIterations[iterationNumber];
       var iteration = new Iteration({
         'number': iterationNumber, 'stories': stories, column: '#done'
       });

spec/javascripts/models/iteration.spec.js

@@ -189,7 +189,7 @@ describe("iteration", function() {
       var that = this;
       expect(function() {
         Iteration.createMissingIterations('#done', that.start, end);
-      }).toThrow("end iteration number must be greater than start iteration number");
+      }).toThrow("end iteration number:1 must be greater than start iteration number:2");
     });
 
     it("should return an empty array when start is undefined and end is number 1", function() {