a UIImageView extension to let the picture-cutting with faces showing better

##Why?

• Have problems showing the resized image previews?
• People in the preview only have chins but not faces?
• A group photo doesn't look well?

Try UIImageView-BetterFace!

Like this:

##How?

1. drag UIImageView+BetterFace.h and UIImageView+BetterFace.m to your project
2. import the .h file
3. add hack_uiimageview_bf(); to your main function
4. add this:[anImageView setNeedsBetterFace:YES];
5. done
6. still have problems? clone the project and see the demo.

##Known issues

• it will be slow to render large-size images, and showing the strange animation
• it may take a lot of memory while reusing the UIImageView

##Other

Any issue and pull request is welcome.