Figuring out how to deal with multiple Accept mediatypes in the header

Currently, liberator contains a bug (https://groups.google.com/forum/#!topic/clojure-liberator/4I95lTCf5D0) that takes the wrong mediatype from the Accept. At the moment, we fix the format for d3.js as csv. The mediatype text/csv must be the first in the :available-media-types