Do not send onSlidingCompleted when value is changed programmatically

[BartoszKlonowski]

This pull request fixes #487
It prevents from sending the onSlidingCompleted event when value is not changed by manual dragging.

This change was implemented according to other platforms so that the behavior is constant across platforms: The controlledValue feature will not trigger any event. Events are reserved for manual dragging or tapping.

Issue487-Fix-Demo.mov

This change has been also reflected in the documentation.

[laurent22]

Isn't it a breaking change?

[BartoszKlonowski]

Isn't it a breaking change?

Hello @laurent22! No, not really. Same as on iOS and other platforms - the programmatic change of value prop should not trigger the onSlidingCompleted. Changing value programmatically is not a sliding so this event would be misleading. Moreover, if developer changes the value programmatically then it should be intentional hence well known that it happened, so no need to notify about it by sending any sliding or dragging-related event.
I hope it does answer your concerns.