Add Auto-Orientation

I've based this work off of @orbanbotond's efforts, but have added
support for RMagick and MiniMagick, and included tests.
Rename auto_orient! to auto_orient to be consistent with other processors

Also add more tests
Merge branch 'pr7'
v1.1.0
Don't process images when quality does not change

Via [carrierwave's wiki](https://github.com/carrierwaveuploader/carrierwave/wiki/How-to%3A-Specify-the-image-quality)