[Python-porting] [RELEASED] six 1.6.0

[Benjamin Peterson]

I'm releasing six 1.6.0. It has a few more backports and another attempt
to solve the great lazy proxy module problem suggested by Diana Clark.

Here's the changelog:

- Raise an AttributeError for every attribute of unimportable modules.

- Issue #56: Make the fake modules six.moves puts into sys.modules
appear not to
  have a __path__ unless they are loaded.

- Pull request #28: Add support for SplitResult.

- Issue #55: Add move mapping for xmlrpc.server.

- Pull request #29: Add move for urllib.parse.splitquery.