Updated the migration guide

@@ -27,16 +27,28 @@ With 4.0, the ones marked as `nullable` will be regular optionals, as the `nonnu
 
 For details, read [Nullability and Objective-C](https://developer.apple.com/swift/blog/?id=25).
 
-#### Simple case
+#### Using the UI*View categories brings no change
 
 SDWebImage 3.x
 ```
-[imageView sd_setImageWithURL:url];
+[imageView sd_setImageWithURL:url placeholderImage:placeholderImage];
 ```
 
 SDWebImage 4.x
 ```
-[imageView sd_setImageWithURL:url];
+[imageView sd_setImageWithURL:url placeholderImage:placeholderImage];
+```
+
+#### Using directly SDWebImageManager
+
+SDWebImage 3.x
+```
+[manager downloadImageWithURL:url options:options: progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) { ... } ];
+```
+
+SDWebImage 4.x
+```
+[manager loadImageWithURL:url options:options: progress:nil completed:^(UIImage *image, NSData *imageData, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) { ... } ];
 ```
 
 ### Entities
@@ -183,4 +195,4 @@ SDWebImage 4.x
 #### UIImage
 - removed `sd_animatedGIFNamed:` or `sd_animatedImageByScalingAndCroppingToSize:`
 - added `isGIF`
-- added `sd_imageData` and `sd_imageDataAsFormat:`. Those methods transform a `UIImage` to the `NSData` representation
\ No newline at end of file
+- added `sd_imageData` and `sd_imageDataAsFormat:`. Those methods transform a `UIImage` to the `NSData` representation