Fixed image ratio while cropping and required explicitly defined Papercrop as a processor

[davidmccoy]

Papercrop is not properly translating Jcrop's cropping information for images that are smaller than the preview image. I applied a previously-submitted JavaScript update to fix this bug.

I also removed the functionality that automatically adds Papercrop to the end of the processor chain. I believe this is a worthwhile improvement for a few reasons:

1. There have also been multiple requests to have Papercrop only process a single style.
2. It is a bit heavy-handed to apply Papercrop to EVERY style without any way of removing it from the processor chain.
3. It also seems unintuitive to have Papercrop automatically added to the end of the processor chain because it hides the Papercrop processor behind "Rails magic."

Thanks for your time!

[rsantamaria]

@davidmccoy Sadly I can't find a way to reproduce the proportions bug without the use of css tricks.

This is a 250x250 image in a preview of 500 pixels wide, without the fix.
Please, could you give me a real example of the bug using one of the test apps?
Thanks!