Remove `use_2to3=True` from setup.py

This removes `use_2to3=True` from `setup.py` and then replaces the `u''` literals with `u('')` function calls, because Python 3.2 doesn't have the `u''` literals (Python 3.3 added it back though).

If we removed support for Python 3.2, we wouldn't need the `u` function. Not that I think it's a big deal.

Not having `use_2to3=True` is nice because then  you can use the raw Python code as-is in Python 3. This means that in a Python 3 virtualenv you can do `pip install -e .` or `python setup.py develop` and then edit the code and see the changes reflected immediately. With `use2to3`, you have to keep rebuilding to pick up changes.

So not having `use_2to3=True` is nicer.

Cc: @Frozenball, @sontek, @aconrad