Support for dynamic ranges

This refactors how we do ranges and implements tuning parameters for a "Render" range and a "Preload" range

AsyncDisplayKit/ASCollectionView.h

@@ -10,6 +10,7 @@
 
 #import <AsyncDisplayKit/ASRangeController.h>
 #import <AsyncDisplayKit/ASCollectionViewProtocols.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
 
 
 @class ASCellNode;
@@ -29,11 +30,24 @@
 @property (nonatomic, weak) id<ASCollectionViewDelegate> asyncDelegate;
 
 /**
- * Tuning parameters for the working range.
+ * Tuning parameters for a range.
  *
- * Defaults to a trailing buffer of one screenful and a leading buffer of two screenfuls.
+ * @param range The range to get the tuning parameters for.
+ *
+ * @returns A tuning parameter value for the given range.
+ *
+ * Defaults to the render range having one sceenful both leading and trailing and the preload range having two
+ * screenfuls in both directions.
  */
-@property (nonatomic, assign) ASRangeTuningParameters rangeTuningParameters;
+- (ASRangeTuningParameters)tuningParametersForRange:(ASLayoutRange)range;
+
+/**
+ * Set the tuning parameters for a range.
+ *
+ * @param tuningParameters The tuning parameters to store for a range.
+ * @param range The range to set the tuning parameters for.
+ */
+- (void)setTuningParameters:(ASRangeTuningParameters)tuningParameters forRange:(ASLayoutRange)range;
 
 /**
  * Initializer.
@@ -153,3 +167,9 @@
 - (void)collectionView:(ASCollectionView *)collectionView didEndDisplayingNodeForItemAtIndexPath:(NSIndexPath*)indexPath;
 
 @end
+
+@interface ASCollectionView (Deprecated)
+
+@property (nonatomic, assign) ASRangeTuningParameters rangeTuningParameters ASDISPLAYNODE_DEPRECATED;
+
+@end