Add ImageIO dep

@@ -17,6 +17,7 @@ Pod::Spec.new do |s|
                    'and performances!'
 
   s.source_files = 'SDWebImage/{SD,UI}*.{h,m}'
+  s.framework = 'ImageIO'
 
   # TODO currently CocoaPods always tries to install the subspec even if the dependency is on just 'SDWebImage'
   #s.subspec 'MapKit' do