Fix UIScrollView+MJExtension.h

replace "respondsToSelector" by "instancesRespondToSelector"

MJRefresh.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
     s.name         = 'MJRefresh'
-    s.version      = '3.1.15.5'
+    s.version      = '3.1.15.6'
     s.summary      = 'An easy way to use pull-to-refresh'
     s.homepage     = 'https://github.com/CoderMJLee/MJRefresh'
     s.license      = 'MIT'

MJRefresh/UIScrollView+MJExtension.m

@@ -21,7 +21,7 @@ + (void)initialize
 {
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
-        respondsToAdjustedContentInset_ = [self respondsToSelector:@selector(adjustedContentInset)];
+        respondsToAdjustedContentInset_ = [self instancesRespondToSelector:@selector(adjustedContentInset)];
     });
 }