Updated Travis CI Config

.travis.yml

@@ -1,3 +1,7 @@
 language: objective-c
+osx_image: xcode7
 xcode_project: Framework/YYWebImage.xcodeproj
-xcode_scheme: YYWebImage
+xcode_scheme: YYWebImage
+
+script:
+- xctool -project Framework/YYWebImage.xcodeproj -scheme YYWebImage build test CODE_SIGN_IDENTITY="" CODE_SIGNING_REQUIRED=NO

YYWebImage/YYWebImageOperation.m

@@ -420,7 +420,7 @@ static NSData *JPEGSOSMarker() {
     }
 }
 
-- (nullable NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
+- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
     if (!cachedResponse) return cachedResponse;
     if (_options & YYWebImageOptionUseNSURLCache) {
         return cachedResponse;