Add newstr object: backport of Py3 str
Consistent names of backported classes: new*
Minor update to docs
More doc updates
Use isinstance(blah, type('')) idiom in test_httplib.py

* TODO: The docs should describe the purpose of this too.
* Is there a cleaner alternative that could be recommended over this?
Tidy up __init__.py files; update docs
Remove support for deprecated ``from future import *`` imports; bump version to v0.6.0-dev
Remove last vestiges of ``from future import *`` from code and comments