Updated travis and README
Merge branch 'postload' of github.com:brmc/django-media-helper into postload
Added management command to resize a single image, and then a couple small things
Added tox environments explicitly for django
Added hook to tools.resizers.resize() to pass an optional filename. In order to get around the problem of image galleries loading a low-quality image, this will eventually provide the mechanism to access an image of known size and quality.
Now passes 'keep' to the quality kwarg for jpegs