Changed to 'baseurl'

When using 'url', date-based paths were being incorrectly overwritten. Changed to 'baseurl' so that the "true" filename stays.

E.g. http://mywebsite.com/wp-content/uploads/2012/13/myfile.jpg was being rewritten to http://blobaddress.com/container/myfile.jpg instead of http://blobaddress.com/container/2012/13/myfile.jpg