jwilling/JNWCollectionView — pull request #128 by kmisiura (2014-12-15 08:40:37+00:00)
Title: More interaction with supplementary views.

Added delegate messages about supplementary views being added and removed from document view:

```objectivec
- (void)collectionView:(JNWCollectionView *)collectionView
willDisplaySupplementaryView:(JNWCollectionViewReusableView *)supplementaryView
ofKind:(NSString *)kind
forsection:(NSInteger)section;

- (void)collectionView:(JNWCollectionView *)collectionView
didEndDisplayingSupplementaryView:(JNWCollectionViewReusableView *)supplementaryView
ofKind:(NSString *)kind
forsection:(NSInteger)section;
```

Implemented methods to get visible supplementary views:

```objectivec
- (NSArray *)visibleSupplementaryViews;

- (NSArray *)visibleSupplementaryViewsForKind:(NSString *)kind;
```