Using the source image's the color space for image decoding (fix SDWebImage#237)

Should fix most system warnings regarding invalid context configurations

Author: matej

SDWebImage/SDWebImageDecoder.m

@@ -18,9 +18,8 @@ + (UIImage *)decodedImageWithImage:(UIImage *)image
     CGSize imageSize = CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef));
     CGRect imageRect = (CGRect){.origin = CGPointZero, .size = imageSize};
 
-    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
+    CGColorSpaceRef colorSpace = CGImageGetColorSpace(imageRef);
     CGContextRef context = CGBitmapContextCreate(NULL, imageSize.width, imageSize.height, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpace, CGImageGetBitmapInfo(imageRef));
-    CGColorSpaceRelease(colorSpace);
 
     // If failed, return undecompressed image
     if (!context) return image;