Fixes a bug in download_object() that would throw an exception if the target directory already exists.

Also cleaned up inconsistencies in naming among the methods that can accept either a storage_object or its name.
These changes are based upon PR #148.
Merge pull request #149 from EdLeafe/working

Restores several reverted commits, and fixes some others
Fixed a bug noticed in #69 in which the parameters to the swiftclient connection object were incorrect.
Merge branch 'working' into dev
Merge branch 'dev' of github.com:rackspace/pyrax into dev