Added support for animations in the CoordinatorLayout

[wdullaer]

With these changes this FloatingActionButton will behave just like the design library supplied one: it will hide automatically when using an AppBarLayout and it will scroll up when a design library SnackBar is shown. No additional code required.

The hack is rather dirty: the FabBehavior should ideally belong to the com.melnykov.fab package. Unfortunately the method getMinimumHeightForVisibleOverlappingContent() of the AppBarLayout has package scope, so we need to add this class to android.support.design.widget If google makes this method public in an update to the design library, this should be refactored.