添加防盗链referer review by 枪兵

 Pod::Spec.new do |s|
   s.name = 'SDWebImage'
-  s.version = '1.0.5'
+  s.version = '1.0.6'
   s.platform = :ios, '8.0'
   s.license = 'MIT'
   s.summary = 'Asynchronous image downloader with cache support with an UIImageView category.'

@@ -42,6 +42,7 @@
     if ((self = [super init])) {
         _imageCache = [self createCache];
         _imageDownloader = [SDWebImageDownloader sharedDownloader];
+        [_imageDownloader setValue:@"yohobuy.com" forHTTPHeaderField:@"Referer"];
         _failedURLs = [NSMutableSet new];
         _runningOperations = [NSMutableArray new];
     }