Refactored the layout methods.
Pass a reference to the app instance to all the other classes.
Fire the overview:changed event.
Listen on the app instance for the navigation:changed event.
Bubble the navigation:changed event to the app instance.
Reposition the slides when overview mode changes.
Remove the 'present' CSS class from the previous subSection.
Specify the direction of the navigation when it changes.
When the navigation changes, update the position of the sections or subsections.