Remove Support for iOS 7 (#2930)

* Drop support for iOS 7

* Copy reference images

* Update deployment for sample projects

* Update version

* Update "Life Without Cocoapods"

AsyncDisplayKit/TextKit/ASTextKitContext.h

@@ -9,6 +9,7 @@
 //
 
 #import <UIKit/UIKit.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
 
 /**
  A threadsafe container for the TextKit components that ASTextKit uses to lay out and truncate its text.
@@ -16,6 +17,7 @@
  This container is the sole owner and manager of the TextKit classes.  This is an important model because of major
  thread safety issues inside vanilla TextKit.  It provides a central locking location for accessing TextKit methods.
  */
+AS_SUBCLASSING_RESTRICTED
 @interface ASTextKitContext : NSObject
 
 /**
@@ -38,7 +40,7 @@
 
  Callers MUST NOT keep a ref to these internal objects and use them later.  This WILL cause crashes in your application.
  */
-- (void)performBlockWithLockedTextKitComponents:(void (^)(NSLayoutManager *layoutManager,
+- (void)performBlockWithLockedTextKitComponents:(AS_NOESCAPE void (^)(NSLayoutManager *layoutManager,
                                                           NSTextStorage *textStorage,
                                                           NSTextContainer *textContainer))block;