Added jquery.serializeJSON [author]

https://github.com/marioizquierdo/jquery.serializeJSON
This library helps serializing a form into a JavaScript object, including nested keys.

I added the last version, and other 2 old versions: (latest 1.2.x, 1.1.x and 1.0.x):
 * https://github.com/marioizquierdo/jquery.serializeJSON/blob/1.2.0/jquery.serializeJSON.min.js
 * https://github.com/marioizquierdo/jquery.serializeJSON/blob/1.1.0/jquery.serializeJSON.min.js
 * https://github.com/marioizquierdo/jquery.serializeJSON/blob/1.0.2/jquery.serializeJSON.min.js

Please add to the CDN, then I will update my README to include installing from CDN in the instructions.

Thanks!