Update vendor/backbone to v1.3.3.

vendor/backbone/backbone.js

@@ -1,4 +1,4 @@
-//     Backbone.js 1.3.2
+//     Backbone.js 1.3.3
 
 //     (c) 2010-2016 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 //     Backbone may be freely distributed under the MIT license.
@@ -44,7 +44,7 @@
   var slice = Array.prototype.slice;
 
   // Current version of the library. Keep in sync with `package.json`.
-  Backbone.VERSION = '1.3.2';
+  Backbone.VERSION = '1.3.3';
 
   // For Backbone's purposes, jQuery, Zepto, Ender, or My Library (kidding) owns
   // the `$` variable.

vendor/backbone/test/collection.js

@@ -1898,7 +1898,7 @@
       assert.deepEqual(changed.merged, []);
       assert.ok(changed.removed.length === 2);
 
-      assert.ok(changed.removed.indexOf(model) > -1 && changed.removed.indexOf(model2) > -1);
+      assert.ok(_.indexOf(changed.removed, model) > -1 && _.indexOf(changed.removed, model2) > -1);
     });
     collection.remove([model, model2]);
   });

vendor/backbone/test/view.js

@@ -14,6 +14,11 @@
         className: 'test-view',
         other: 'non-special-option'
       });
+    },
+
+    afterEach: function() {
+      $('#testElement').remove();
+      $('#test-view').remove();
     }
 
   });