Fixes #221: Allow select, radio, checkbox to be used outside a form

* Update select editor to `setOptions` handed to initialize. This provides
  similar functionality to both radio and checkbox. (They extend it)
* Update unit tests for radio and checkbox to test that empty options can
  be intialized
* Add unit test for new select behaviour.

This should update the library to once again support using a select editor
outside of a form.