[LIBCLOUD-638] Add, document and test for headers to ``upload_object_via_stream``, and similar methods to enable supporting CORS (or other) headers in the cloudfiles driver:
https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS#Access-Control-Allow-Origin
http://docs.rackspace.com/files/api/v1/cf-devguide/content/Assigning_CORS_Headers_to_Requests-d1e2120.html
Document something that affects a full usage of a bytes iterator but I have no idea on the correct fix for.
e.g. bytes(37) returns 37 null bytes...
Consistently order as :param arg: then :type arg: (if there's a higher level coding convention I'll happily swap the other half of this file instead).