Add 'combobox-selected' class before triggering change events.

[jzamanski]

Allows change event handler to call combobox('toggle') to clear the combobox.

[jzamanski]

Baby's first pull request. Sort of just wanted to see how PR's work. In any case, I'm binding to the change event on the source, 'consuming' the selected element, and then want to clear/reset the combobox. Since the 'combobox-selected' class is being added after the change event is fired, there's no clean way to clear/reset the combobox besides manually removing the class from the container. This was my attempt to fix that / make it do what I wanted.

[thephw]

I think this will likely get deferred to the 2.0 release. Going to work to add and document publicly accessible events to allow people to customize the functionality similar to other bootstrap control at different points in the workflow.