Fix errors with Python 3.3.2 on Ubuntu 13.10

I installed larry by cloning the git repository, then using `pip3 install --user --editable` with the path to the cloned repo.

After doing so, I was unable to `import la` in IPython 0.13.2 and Python 3.3.2 without making the changes in this one commit.

It seems others have contributed Python 3–related changes to the source. I can't see any indication that Python 3 is "officially" supported by larry, but it seems strange that others would be running it on Python 3 without having also encountered, and fixed, these errors.