Fixed issue when using $.extend to merge defaultOptions and options

Hi.

For the moment the return of  `jQuery.extend` is `Object`. This is an issue when you want to merge some default options and options into a new empty object (you can see an example at http://api.jquery.com/jQuery.extend/#example-2).

I updated the test to reproduce the issue and fixed it by changing the return type of `$.extend` to `any`

Olivier