Add support for jQuery 3.0

[abzainuddin]

The jqXHR api has changed: https://jquery.com/upgrade-guide/3.0/#ajax. The jqXHR error and success functions have been removed, which breaks calls to xhrFirstTry.error and xhrFirstTry.success.

[SpaceK33z]

This will require a complete refactoring. jQuery 3.0 uses spec-compliant Promises, which is very nice, but also a lot more difficult to hack.