Moved the openScroller() and closeScroller() calls out of Region.openPage and Region.closePage method to the Scrollable mixin. It should rightfully be present in the mixin only. Removed unncessary checks to see if scrolling is enabled and if the method openScroller and/or closeScroller is present because it is not necessary within the context of the mixin. Directly used "this" instead of currentPage and nextPage as used from within the Region methods because this is mixed-in inside the context of the PageView.

Fixed a bug, where the pagechange event handler was getting bound multiple times because it was attached on the document and was getting attached on every openPage() call. Replaced it with .one() technique.

Added more docs.