Support one column in a hacky way.
Support one column in a hacky way.

tianxiao12345/CHTCollectionViewWaterfallLayout,SummerHanada/CHTCollectionViewWaterfallLayout,809848367/CHTCollectionViewWaterfallLayout,cstars135/CHTCollectionViewWaterfallLayout,goodheart/CHTCollectionViewWaterfallLayout,lonelyplanet/TE-CHTCollectionViewWaterfallLayout,imjerrybao/CHTCollectionViewWaterfallLayout,imjerrybao/CHTCollectionViewWaterfallLayout,iguchunhui/CHTCollectionViewWaterfallLayout,boherna/CHTCollectionViewWaterfallLayout,809848367/CHTCollectionViewWaterfallLayout,chiahsien/CHTCollectionViewWaterfallLayout,tianxiao12345/CHTCollectionViewWaterfallLayout,goodheart/CHTCollectionViewWaterfallLayout,BlessNeo/CHTCollectionViewWaterfallLayout,BlessNeo/CHTCollectionViewWaterfallLayout,SummerHanada/CHTCollectionViewWaterfallLayout,chiahsien/CHTCollectionViewWaterfallLayout,cstars135/CHTCollectionViewWaterfallLayout,iguchunhui/CHTCollectionViewWaterfallLayout