Media.List: no pisar 'collection' en el success de ajax.

Es una solución temporal a #2.

Signed-off-by: Adrian Pardini <github@tangopardo.com.ar>

models/Media.js

@@ -78,7 +78,8 @@ Media.Model = Backbone.Model.extend({
         }
     },
     defaults: {
-        _id: null,
+        _id: '',
+        stat: {},
         file: "None",
         name: "",
         audio: "None",
@@ -184,6 +185,64 @@ Media.List = Media.Model.extend ({
         duration: 0,
         pos: 0,
     },
+
+    // Set a hash of model attributes, and sync the model to the server.
+    // If the server returns an attributes hash that differs, the model's
+    // state will be `set` again.
+    save: function(key, val, options) {
+      var attrs, success, method, xhr, attributes = this.attributes;
+
+      // Handle both `"key", value` and `{key: value}` -style arguments.
+      if (key == null || typeof key === 'object') {
+        attrs = key;
+        options = val;
+      } else {
+        (attrs = {})[key] = val;
+      }
+
+//XXX:
+      // If we're not waiting and attributes exist, save acts as `set(attr).save(null, opts)`.
+      if (attrs && (!options || !options.wait) && !this.set(attrs, options)) return false;
+
+      options = _.extend({validate: true}, options);
+
+      // Do not persist invalid models.
+      if (!this._validate(attrs, options)) return false;
+
+      // Set temporary attributes if `{wait: true}`.
+      if (attrs && options.wait) {
+        this.attributes = _.extend({}, attributes, attrs);
+      }
+
+      // After a successful server-side save, the client is (optionally)
+      // updated with the server-side state.
+      if (options.parse === void 0) options.parse = true;
+      success = options.success;
+      options.success = function(model, resp, options) {
+        // Ensure attributes are restored during synchronous saves.
+        model.attributes = attributes;
+        var serverAttrs = model.parse(resp, options);
+//XXX:
+        delete serverAttrs['collection'];
+        if (options.wait) serverAttrs = _.extend(attrs || {}, serverAttrs);
+        if (_.isObject(serverAttrs) && !model.set(serverAttrs, options)) {
+          return false;
+        }
+        if (success) success(model, resp, options);
+      };
+
+      // Finish configuring and sending the Ajax request.
+      method = this.isNew() ? 'create' : (options.patch ? 'patch' : 'update');
+      if (method === 'patch') options.attrs = attrs;
+      xhr = this.sync(method, this, options);
+
+      // Restore attributes.
+      if (attrs && options.wait) this.attributes = attributes;
+
+      return xhr;
+    },
+
+
 });
 
 Media.Universe = Media.Collection.extend ({