Change Submit behavior

This PR changes what happens when the user click Submit. instead of POSTing the generated link info directly to a remote form, it does one (or both) of two things:

* Appends the generated form fields to a form of the developer's choosing (specified either in the plugin options or the data-target attribute of the element that triggered the modal popup)
* Fires an event with the result data that the developer can handle any number of ways

I think it's far more flexible and elegant this way. Feel free to try out the branch before pulling; the spec/internal app makes it easier to see what's changed.