changed the content-type return again and added a unit test.
changed the content-type return again and added a unit test.

emonty/pyos,rackspace/pyrax,opsdisk/pyrax,sivel/pyrax,briancurtin/pyrax,ddaeschler/pyrax,EdLeafe/pyrax,pratikmallya/pyrax,naemono/pyrax,0dataloss/pyrax,mandx/pyrax,vikomall/pyrax,rackerlabs/heat-pyrax,roelvv/pyrax