Simple directory upload

Tested by uploading boto/docs directory to DreamObjects with a 'boto' prefix:

import boto
import sys

dhoc = boto.connect_dreamobjects(sys.argv[1], sys.argv[2])
b = dhoc.get_bucket('testbucket')
bk = boto.s3.key.Key(b)
bk.set_contents_from_dirname(
    dirname='docs',
    prefix='boto',
    policy='public-read',
)