fix(radio): radio-button should only emit change event if native input does.

[devversion]

• The radio-button should only emit a change event, when the native input does.
  This ensures that the radio-button matches its behavior with the native radio buttons.
• The button-toggle should only emit a change event, when the native input does.
  This ensures that the button-toggle matches its behavior with the native visual hidden input.
  Notice that the button-toggle sets the input type differently based on the type of the toggle.

Breaking Changes:

• radio-button will no longer emit change event on de-select
  
  (Matches native behavior)
• button-toggle will no longer emit change event on de-select when type is set to radio
  
  (Matches native behavior)

Fixes #791

[jelbourn]

The changes look good, but we probably need to do the same thing to button-toggle. Do you want to do a pass on that as well?

[devversion]

@jelbourn Done! Also added some tests for the change event on the button-toggle, because the behavior changes due different modes of the button-toggle.

[jelbourn]

@devversion LGTM, just needs rebase

[devversion]

@jelbourn Done.

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