Slim down the docker image
Slim down the docker image

This doesn't make it small by any means -- it's still 1.7GB -- but the
previous version was 5GB, so it's miles better.

ucsc-mus-strain-cactus/Comparative-Annotation-Toolkit,ComparativeGenomicsToolkit/Comparative-Annotation-Toolkit,ComparativeGenomicsToolkit/Comparative-Annotation-Toolkit