对iOS7的支持问题

修复一个低级错误：将containsString:换为rangeOfString:

MJRefresh.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
     s.name         = 'MJRefresh'
-    s.version      = '3.1.8'
+    s.version      = '3.1.9'
     s.summary      = 'An easy way to use pull-to-refresh'
     s.homepage     = 'https://github.com/CoderMJLee/MJRefresh'
     s.license      = 'MIT'

MJRefresh/NSBundle+MJRefresh.m

@@ -43,7 +43,7 @@ + (NSString *)mj_localizedStringForKey:(NSString *)key value:(NSString *)value
         if ([language hasPrefix:@"en"]) {
             language = @"en";
         } else if ([language hasPrefix:@"zh"]) {
-            if ([language containsString:@"Hans"]) {
+            if ([language rangeOfString:@"Hans"].location != NSNotFound) {
                 language = @"zh-Hans"; // 简体中文
             } else { // zh-Hant\zh-HK\zh-TW
                 language = @"zh-Hant"; // 繁體中文