Moved finishing callback to ProgressStepChangeListener; added method …

[MorANDarty]

…"nextTo(position:Int)" for moving some position.

[GeniusRUS]

Hello MorANDarty! Thanks for the pull request. Changing the separate callbacks for position change and end progress is a good idea. But the change from stepTo has already been implemented as part of the changes according to issue #6 , implemented in the commit b81cd5e in /develop branch. I plan to release next release will be soon. I suggest you remove the changes with stepTo, keeping the changes with the merging of callback methods