Added a scale mode to the center controller and an example project

Added a center scale mode which is similar in functionality to the menu effect seen in https://github.com/romaonthego/RESideMenu but built on top of ViewDeck's foundation.

There are still some bugs when you try to make changes on the fly, but it works pretty well when set up like in the example. Might be a good jumping off point. You can enable the scale mode just by setting the centerScale property to something like 0.5.