Pass step options through to onchange and onbeforechange callbacks

Needed to be able to pass through some data from the initial step options json to use in the `onchange` / `onbeforechange` callbacks.

I added the `options` argument after the `targetElement` argument rather than replacing it outright to maintain backwards compatability, and also update the docs and version number for these changes (to make it clear that older versions will not have access to the options argument)