Raise deployment target to iOS 9 (#743)

https://github.com/TextureGroup/Texture/pull/743

Manually merged since I forgot to retarget that diff onto master before merge

examples_extra/SynchronousConcurrency/Sample/RandomCoreGraphicsNode.m

@@ -86,7 +86,7 @@
 
 - (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
 {
-  [_textNode measure:constrainedSize];
+  [_textNode layoutThatFits:ASSizeRangeMake(CGSizeZero, constrainedSize)];
   return CGSizeMake(constrainedSize.width, 100);
 }