Not sure about this part.

* `@property (nonatomic, readwrite, weak) LFBlurTarget blurTarget;`
* `+[LFBlurTarget targetWithLayer:]`
* `+[LFBlurTarget targetWithLayer:bounds:position:anchorPoint:frame:]`
* `+[LFMutableBlurTarget targetWithLayer:bounds:position:anchorPoint:frame:]`
… :+1: ? :-1: ?