Merge latest master and update Layout headers

AsyncDisplayKit/Layout/ASInsetLayoutSpec.h

@@ -10,6 +10,8 @@
 
 #import <AsyncDisplayKit/ASLayoutSpec.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  A layout spec that wraps another layoutable child, applying insets around it.
 
@@ -33,8 +35,10 @@
 
 /**
  @param insets The amount of space to inset on each side.
- @param child The wrapped child to inset. If nil, this method returns nil.
+ @param child The wrapped child to inset.
  */
 + (instancetype)insetLayoutSpecWithInsets:(UIEdgeInsets)insets child:(id<ASLayoutable>)child;
 
 @end
+
+NS_ASSUME_NONNULL_END