SelfSizingWaterfallCollectionViewLayout mandates `numberOfSectionsInCollectionView:` even though it is an optional method in the DataSource protocol.

[fatuhoku]

-[MakeEatSeeUI.RecipeWaterfallViewController numberOfSectionsInCollectionView:]: unrecognized selector sent to instance 0x7fc243d128e0'
*** First throw call stack:

[adamwaite]

Cool, had always though it was requires since it's required for UITableViews. I'll get around to this.

[fatuhoku]

Thanks @adamwaite :)