rotateimage.hs will not build with lts-8.21

The Repa code uses repa-devil, and the latest version of that package requires transformers <0.5, which requires base <4.9. But the stack.yaml lists the resolver as lts-8.21, which has base of 4.9.1.

Need to switch to using repa-io, friday-devil, or JuicyPixels-repa.