Overhaul ASDataController and extensively test ASTableView.

This diff resolves all known consistency issues with ASTableView and ASCollectionView.
It includes significantly more aggressive thrash-testing in ASTableViewStressTest,
which now passes on a variety of device and simulator configurations.  It also updates
the unit tests run on every commit to ensure any regression is caught quickly.

A few of the salient changes in this diff:
- ASTableView now uses Rene's ASCollectionViewLayoutController, and actually uses a
UICollectionViewFlowLayout without any UICollectionView.  This resolves an issue where
ASFlowLayoutController was generating slightly out-of-bounds indicies when programmatically
scrolling past the end of the table content.  Because the custom implementation is likely
faster, I will revisit this later with profiling and possibly returning to the custom impl.
- There is now a second copy of the _nodes array maintained by ASDataController.  It shares
the same node instances, but this does add some overhead to manipulating the arrays. I've
filed a task to follow up with optimization, as there are several great opportunities to
make it faster.  However, I don't believe the overhead is a significant issue, and it does
guarantee correctness in even the toughest app usage scenarios.
- ASDataController no longer supports calling its delegate /before/ edit operations.  No
other class was relying on this behavior, and it would be unusual for an app developer to
use ASDataController directly.  However, it is possible that someone with a custom view
that integrates with ASDataController and ASRangeController could be affected by this.
- Further cleanup of organization, naming, additional comments, reduced code length
wherever possible.  Overall, significantly more accessible to a new reader.

AsyncDisplayKit/Details/ASDataController.h

@@ -70,25 +70,21 @@ typedef NSUInteger ASDataControllerAnimationOptions;
 /**
  Called for insertion of elements.
  */
-- (void)dataController:(ASDataController *)dataController willInsertNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 - (void)dataController:(ASDataController *)dataController didInsertNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 
 /**
  Called for deletion of elements.
  */
-- (void)dataController:(ASDataController *)dataController willDeleteNodesAtIndexPaths:(NSArray *)indexPaths withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 - (void)dataController:(ASDataController *)dataController didDeleteNodesAtIndexPaths:(NSArray *)indexPaths withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 
 /**
  Called for insertion of sections.
  */
-- (void)dataController:(ASDataController *)dataController willInsertSections:(NSArray *)sections atIndexSet:(NSIndexSet *)indexSet withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 - (void)dataController:(ASDataController *)dataController didInsertSections:(NSArray *)sections atIndexSet:(NSIndexSet *)indexSet withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 
 /**
  Called for deletion of sections.
  */
-- (void)dataController:(ASDataController *)dataController willDeleteSectionsAtIndexSet:(NSIndexSet *)indexSet withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 - (void)dataController:(ASDataController *)dataController didDeleteSectionsAtIndexSet:(NSIndexSet *)indexSet withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;
 
 @end
@@ -117,7 +113,7 @@ typedef NSUInteger ASDataControllerAnimationOptions;
  *  Designated iniailizer.
  *
  * @param asyncDataFetchingEnabled Enable the data fetching in async mode.
- 
+ *
  * @discussion If enabled, we will fetch data through `dataController:nodeAtIndexPath:` and `dataController:rowsInSection:` in background thread.
  * Otherwise, the methods will be invoked synchronically in calling thread. Enabling data fetching in async mode could avoid blocking main thread
  * while allocating cell on main thread, which is frequently reported issue for handling large scale data. On another hand, the application code
@@ -127,7 +123,11 @@ typedef NSUInteger ASDataControllerAnimationOptions;
  */
 - (instancetype)initWithAsyncDataFetching:(BOOL)asyncDataFetchingEnabled;
 
-/** @name Initial loading */
+/** @name Initial loading
+ *
+ * @discussion This method allows choosing an animation style for the first load of content.  It is typically used just once,
+ * for example in viewWillAppear:, to specify an animation option for the information already present in the asyncDataSource.
+ */
 
 - (void)initialDataLoadingWithAnimationOptions:(ASDataControllerAnimationOptions)animationOptions;