Fix #1339 - Add Backbone.View#destroy.

backbone.js

@@ -1183,6 +1183,13 @@
       return this;
     },
 
+    // **destroy** should clean up any references created by this view,
+    // preventing memory leaks.  The convention is for **destroy** to always
+    // return `this`.
+    destroy: function() {
+      return this;
+    },
+
     // Remove this view from the DOM. Note that the view isn't present in the
     // DOM by default, so calling this method may be a no-op.
     remove: function() {