Change private variables into protected ones.

Hey there!

I wanted to change how the imagecrop functionality worked a little, so I tried to do a subclass of the ImageCrop class. That let me override the code in places, except that with all of the properties private, they were hidden from my subclass - I had to go through and change them to protected to work.

There's not much reason not to have the properties as protected instead of private, and it would make folks working with your code have an easier time of it.

Thanks!

(I'm planning on a patch later on, but I wanted to start up the ticket to remind me.)

(Awesome module, btw.)