Fixed prototype extends models to the particular extend model.

That will be able to extend a particular class.
For example:
```
define([
	'backbone-model-file-upload'
], function(
	FileModel
) {
	'use strict';
        
	var CsvFileModel = Backbone.FileModel.extend({
              // Or you can use: CsvFileModel = FileModel.extend ...
        });
});

```
After this code CsvFileModel will be able to save files. Now we have to connect backbone-model-file-upload extend all models of project — it's wrong way, and came across this approach to unexpected errors of the common method 'save()'.

Sorry for my bad English.