Can't set CORS headers via container.upload_object_via_stream()

Would be nice to have the ability to set Cross-Origin Resource Sharing (CORS) headers, and probably other headers too when using `container.upload_object_via_stream()` without subclassing and overriding several lower level functions.

References:
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

Ran into this migrating a project from Rackspace cloudfiles which allows setting of CORS headers.